- “Don't you remember? Your ape-like incompetence drove my father insane!”
- ―Frank Grimes, Junior
Homer Simpson is subject to several murder attempts. Sideshow Bob is roped in to help him find the perpetrator, who is revealed to be Junior, Homer's mechanic. When Homer questions how Frank Grimes had a son when he was not married, he explains that his dad "happened to like hookers," and one of them gave birth to him.
Homer "killed" his father by driving him insane, so Junior was trying to avenge his death. He even "killed" Duffman. He also becomes more infuriated in each passing moment he shares with Homer (just like his father). He has yet to reappear in future episodes.
Non Canon Appearances
In Simpsons Comic #108's story Big House Homer, Homer was framed by Mr. Burns for dealing nuclear weapons and arrested. He was cellmates with Sideshow Bob and they escaped from jail, by going through a tunnel in a cell occupied by a masked prisoner, who Bob mentioned was "a big psycho." The three fell into Mr. Burns's secret lair, where the mysterious prisoner was revealed to be Grimes. Frank Grimes then angrily revealed his identity, though Homer forgot who he was due to having "a lot of things occurring", and then attempted to throttle Homer upon mentioning how his dad died before someone stumbled upon it. Sideshow Bob then fell on him and both were knocked unconscious. Homer was cleared of his charges, whilst Bob and Grimes were presumably sent back to prison.
- He looks very similar to his father, but without glasses, slightly baggy eyes, mossy hair and a different nose shape.