Charlie often exhibits difficulty reading and writing, and is often accused of being illiterate or dyslexic by other characters. Mac even went as far as claiming "No one understands the subtleties of Charlie's retardation better than me." (The Gang Gets Held Hostage)
Charlie's literacy, or lack thereof, is never really addressed in Season One. Generally speaking, he is presented as being more intelligent than he will be in later seasons. He is even seen reading on two separate occasions in "Charlie Has Cancer".
Season Two
Charlie writes a script for a "jihad video" that The Gang wants to use to threaten Ari Frankel, but Dennis refuses to read it, saying that it is "riddled with spelling errors," and speaks gibberish meant to sound like Arabic instead. (The Gang Goes Jihad)
Charlie was unable to read his job listed on paper after blowing up a building (The Gang Goes Jihad), so he got Mac to read it for him. The words were "Interstate" and "sanitation". (The Gang Gives Back)
Charlie wrote an incoherent script for Dennis' TV commercial: "Hello fellow American. This you should vote me. I leave power. Good. Thank you, thank you. If you vote me, I'm hot. Taxes, they'll be lower... son. The Democratic vote is the right thing to do Philadelphia, so do.". (The Gang Runs for Office)
Charlie can not read a note left by Frank: Charlie: "Okay, meet... it starts out meet... um"; Dennis: (takes note) "'Meet me in the parking garage. -Frank.' You clearly have a learning disability, dude". (The Gang Runs for Office)
Season Three
Charlie kidnapped a baby from Mac and Dee, and leftthis note: "Taked Baby. Meet at later bar. Night or day sometime." (The Gang Finds a Dumpster Baby)
Charlie wrote a note in the vents that Frank read: "If here by now then bad place be. Trouble time for you when heat comes." (The Gang Gets Held Hostage)
Charlie misread a contract that resulted in his putting the bar at risk of being lost in a contest, misreading the word PRIZE as PRIDE. (The Gang Dances Their Asses Off)
For some reason, Charlie is familiar with the word "disintegrated" [4x5]. Probably, he heard it in "Law & Order".
In the "list of demands" that Charlie and Mac leave in lieu of a last will and testament, Charlie demands that "[his] ashes are to be made into a tea and dranken by every wan in bar." [4x5]
Charlie has a stalking notebook, where he keeps all the Waitress' "whereabouts". For some reason, Dee was able to read it (after she stole it) - but that's okay, because Charlie have backups for it. [4x7]
Some fans have suggested that Charlie's freakout over Pepe Silvia might be due to him not being able to read the word "Pennsylvania". However, Mac points out to Charlie in the episode, "Not only do all of these people exist, but they have been asking for their mail on a daily basis!". Additionally, staff writer Scott Marder was asked directly and denied the theory.
Charlie was unable to write clear lyrics to his musical, and needed help from Artemis: Charlie: "She also transcribed my work into a format you might find more legible."; Dee: "Or literate, she added words to it."(The Nightman Cometh)
Season Five
Kitten Mittons
When Charlie tries to argue with The Lawyer about contract law, The Lawyer remarks that not only does Charlie not know anything about the law, "It seems like you have a tenuous grasp on the English language in general." Charlie responds to this by saying "Filibuster," but cannot tell The Lawyer what that word means when The Lawyer asks Charlie to define it for him. (The Gang Exploits the Mortgage Crisis)
Charlie turned on the CLOSED sign in front of the bar every morning, because he believed it says COORS. (The Great Recession)
Charlie does not know the meaning of the word "illiteracy". Later in that same episode, Dee asks a therapist to give Charlie an intervention "because he's totally illiterate" -- Charlie denies that he can't read or write, he says he just doesn't like to. (The Gang Gives Frank an Intervention)
In a somewhat surprising moment of literacy, Charlie manages to write a perfectly formed "H" on a box he has put a hornet's nest into, even though he is writing on the side of the box facing away from him, forcing him to write backwards and upside down in relation to him (It should be noted that writing a H "backwards and upside down" is the same as writing a regular H). (It's also a bit striking that he knows that the word "hornet" begins with an "H".) In that same episode, however, his difficulty with language raises its head again, as he cannot understand the word "philanthropist" and ends up telling his date that he is a "full-on rapist." (The Waitress is Getting Married)
Charlie's Kitten Mittens commercial was entitled KITTEN MITTONS. Later on, after trying to speak "lawyer talk", he grabs his lapels and says he's made himself "perfectly redundant", something The Lawyer is eager to agree with. (Paddy's Pub: Home of the Original Kitten Mittens)
Charlie was unable to read a carnival sign in front of the Waitress that said, "SpeedPitch: HOW FAST CAN YOU THROW?" (The D.E.N.N.I.S. System)
Season Six
Charlie tries to search the Internet for the word "hockey" but insists that the keyboard has no "H" key. (Mac's Big Break)
Charlie has typed the Waitress in his mobile's memory as "Wicksox" or something. He was ashamed before Mac, so he blamed a "smart type" of his phone by saying "it tries to complete the word for you". (Deleted Scene for Mac and Charlie: White Trash)
Charlie's book, which contains all his "dreams and aspirations" (which are mostly in pictures and symbols), entitled as "Dram bok" - this should stand for "Dream book". (Charlie Kelly: King of the Rats)
Season Seven
Charlie barfs a bunch of fake blood on his date (which was a set up to actually end up being Frank's date) in the back of the limo that Frank is driving. Even though it ought to be obvious that you shouldn't ingest the capsules, let alone "swallow a bunch of blood 'capslets'", as Charlie then claims to have done earlier, Charlie wouldn't have been able to coherently read any warning on the packaging due to his illiteracy. He also claims to have a "touch of consumption", though is able to accurately use the word "constituent". (Frank's Pretty Woman)
The question that Charlie wrote for Chardee MacDennisreads as follows: "Dennis is asshole. Why Charlie hate?" (the answer being, of course, "Because Dennis is a bastard man.") Charlie denies that he wrote it, but Mac says it has to be him, because "How many illiterates are there here?" As soon as Dennis answers, Charlie remembers that he wrote the card. (Chardee MacDennis: The Game of Games)
Probably, it was written something like this :
Denis is ashole. Y Charlee hat? (Becauze Denis is a bastardt man!)
Charlie misread a door marked "Brett DeLawter, A Dental Corporation" as "Brett DeLawyer, A Denial Correlation". Mac remarks that this was pretty good, showing that Charlie might be working on reducing his illiteracy. (Pop-Pop: The Final Solution)
Charlie keeps a list of things that he regularly does for The Waitress: for instance, he watches her bike so it doesn't get stolen (and barks at every "suspicious" person like a dog), puts vitamins in her shampoo so her hair doesn't fall out, and tests her food so it doesn't get poisoned - of course, it's all in weird paintings. For some reason, Dennis is aware about that. When Frank tries to use the list to do tasks for The Waitress that Charlie was doing, he misreads it (understandably) and does the tasks incorrectly: for example, he thinks it says that he should put rat poison in her shampoo. (Charlie and Dee Find Love)
Here's a part of Bonnie Kelly's speech from her cancer fundraiser that Charlie wrote: "Give me money. Money me. Money now. Me a money needing a lot now." (Charlie's Mom Has Cancer)
When Frank takes on Charlie as his "right-hand man" for his return to the company he founded, both Mac and Dennis state that Charlie cannot read. However, Charlie does actually prove at least somewhat competent at the job, as he is able to keep track of Frank's busy schedule, apparently writing it down in an appointment book (presumably in the same mixture of drawings and fractured phrases he has used before.) (Frank's Back in Business)
Charlie wants to know who he'll be "persecuting" (instead of prosecuting) in the trial. He immediately follows up Dee's remark on this mistake with the word "irregardless," which does not exist. Another point in the episode that demonstrates Charlie's minimal grasp of the English language is when he replaces the words "distinguished colleagues" with "distinguished collies. (Reynolds vs. Reynolds: The Cereal Defense)
Season Nine
In an animated fantasy of his life with The Waitress, Charlie teaches the many children he and The Waitress have had the game Night Crawlers with a chart labeled "NITE KROLLER RULEZ" (The Gang Saves the Day)
When he is given a placebo smart pill, Charlie begins displaying a startlingly heightened intelligence, due to his access to audio books. Dennis remarks that "any idiot" can listen to a book, but is shut down when Charlie accurately describes the placebo effect. He can understand Shakespeare's stance on brevity, speak much more articulately, and evidently has taken up speaking Mandarin. However, by the end of the episode, it's exposed that most of Charlie's intelligence was either forgotten or made up: He's been speaking gibberish, believes he's invented a way for "Spydars" to talk to cats, and forgets how to say "Placebo", a word he accurately used a day before. His mathematical equations shown are "4 + 4= 17 %" and "X = 9 + 9 = box (that's where the cat goes)". (Flowers for Charlie)
Season Ten
Charlie apparently does not recognize cursive writing as writing, referring to it as "weird squiggly lines." (Mac Kills His Dad)
Charlie takes the survey to provide answers for the game show "Family Fight", including one that reveals his difficulty with understanding the meaning of words: he provides the answer "Bride" for the question "Name something people groom themselves with, because "you can't become a groom, or be groomed, without a bride." (The Gang Goes on Family Fight)
It's pointed out that Charlie signed "Paddy's Succession Plan" as what appears to be "Chrundle". Charlie claims "I was going by Chrundle at the time", but Mac says he was just trying to write "Charlie" and failing. (Frank Retires)
When interviewing potential roommates with Mac, Charlie is wearing his reading glasses, but any time he puts pen to paper, he just makes scribbling motions. As it turns out, he's simply drawing cans of cat food to determine how suitable each candidate is. (Frank Falls Out the Window)
Mac describes Charlie as an "illiterate janitor" to an art gallery owner that they want to hold an exhibit of Charlie's artwork. (Dee Made a Smut Film)
Season Twelve
Charlie expresses a great deal of confusion trying to read a map, saying he's not sure how to find north on it; he believes north is wherever up is. He is further confused when Frank explains that north is on the top of the map. (The Gang Goes to a Water Park)
Charlie receives a letter made up of symbols and drawings from his mother, resembling some of the "writing" he's done in episodes like The Nightman Cometh, which suggests that she knows how to "write" in a way he can understand (though he still manages to misunderstand the note he's sent). When he watches the sitcom that Dennis has assembled out of surveillance footage of his mom and Mac's mom, Charlie says "It's cool how the letters fly on the screen", not recognizing the letters as credits. (Old Lady House: A Situation Comedy)
While writing a Valentine's Card for Frank's tapeworm Jerry, Charlie struggles a great deal with writing the message and rhyming. When commanded by Dee under the threat of anthrax to sing her a Valentine's song, he is unable to rhyme simple words (such as rhyming "Dee" with "Beetle" or "I"). (The Gang Tends Bar)
On one of the graphs Charlie has made up for the Waitress, he has written "WORK" in very crude uneven letters, with a backwards "R". (Dennis' Double Life)
Dennis: I'll read the words you wrote. "Hello fellow American. This you should vote me. I leave power. Good. Thank you, thank you. If you vote me, I'm hot." What? "Taxes, they'll be lower... son. The Democratic vote for me is right thing to do Philadelphia, so do." This doesn't make any sense!
Charlie: Alright... then just say whatever you want.
Charlie: Lastly, before I open the bar in the morning, I always make sure to turn on the "Coors" sign, let people know we got ice delicious Coors in the bar, you know, and then that's the last thing I do. Ol' Charlie's done a lot of work around here.
