Pop Pop mistook Charlie for Dennis and asked him to pick up some private belongings that he's had in hiding for a long time. It turned out that these private belongings were all Nazi memorabilia. Rather than return the items to Pop Pop, Charlie kept them. Later, Dee visited Pop Pop. Being repulsed by elderly people, the visit made her vomit. ("The Gang Finds a Dead Guy")
Pop-Pop is in a coma, being kept alive by life support machines. As his last blood relatives, it's left up to Dennis and Dee to decide if he should be taken off life support and allowed to die. Frank, however, tries to get them to keep him alive, because he is seeking a Nazi treasure that Pop-Pop spoke of. The treasure turns out to a picture of a German Shepherd painted by Adolf Hitler, which Charlie had kept on the wall of his apartment until Frank had forced him to take it down. During the course of their deliberations on whether or not to keep Pop-Pop on life support, Dee and Dennis discover a home movie that shows him taking them (when they were 9 years old) to a neo-Nazi summer camp, thus confirming that Pop-Pop remained a Nazi long after he came to America.("Pop-Pop: The Final Solution")
- In Season Eight, he was named after John Landgraf, the president of
- Pop-Pop hates "Jews", and believes that "Kikes" are stealing his stuff.
- Pop-Pop favors Dennis over Dee.
- Pop-Pop wishes to be buried in his Nazi uniform.
- Pop-Pop gets angry when people don't eat his candy.
- In Season One, it's not stated whether Pop-Pop is Dennis' paternal grandfather or maternal grandfather, but since Frank is later revealed to not be Dennis' biological father ("Dennis and Dee Get a New Dad"), the physical resemblance between Dennis and Pop-Pop would suggest that Pop-Pop is Barbara's father.
- So, Pop-Pop IS Barbara's father, then also he's apparently Donna's father and thus Gail the Snail's grandfather, too. But this contradicts Attorney saying Dennis and Dee are Pop-Pop's sole surviving heirs. Perhaps Barbara and Donna were only half sisters and had different fathers. (Or Max, Donna's husband, is Frank's brother, and thus Donna is only his daughter-in-law. The only mention of a brother for Frank, though, is Geno, in the episode "Frank's Brother")
- Pop-Pop's alias: "War Hero", "King Nazi", "Old Nazi Bitch"
- Close inspection of Pop-Pop's Nazi Uniform reveals that he was part of the Schutzstaffel or 'SS'. Noting the SS runes on his collar, the Silver Totenkopf or "Death's Head" skull on the cap. His rank marked by the three diamonds on his collar and distinctive black uniform show that he was a low ranking gestapo officer or "Untersturmführer".