Mr. Pickels is one of the main characters in Happy Tree Friends. He's Lammy's imaginary (villainous) friend, and they are never seen separated. He's a pickle and the only non-animal character in the show. Character Bio Edit
As seen in his debut episode, A Bit of a Pickle, he is one of the characters to kill other Happy Tree Friends on purpose, which is considered arguable, since he might be imaginary. He seems to like tea parties, and was seen having one with Lammy in the begining of A Bit of a Pickle.
Mr. Pickels (in Lammy's imagination possibly, as he often appears as a normal pickle) wears a top hat and he has a moustache, like Mouse Ka-Boom. Many fans believe that Mr. Pickels is the representation of a repressed dark half of Lammy, similar to Flippy's "flipped out" state.
Although he is similar to Flippy, the difference is that Mr. Pickels presents a new opportunity for the show to set up unique scenarios, assuming Lammy is a schizophrenic, where one character is blamed for another's actions, leading to some awkward results.
Mr. Pickels could also be jealous of other people around Lammy, and thus hate on them, since he would want all of her attention to himself rather than let her have real friends. After he kills someone, he goes back to his normal pickle form, which gets Lammy framed.
He is also an antagonist of the series, who murders people (such as Petunia). Lumpy thought Lammy had murdered Flaky when it was really Mr. Pickels. He is one of the most violent characters in the series (along with Flippy, Tiger General, and The Ants).
For now, Mr. Pickels is the only non-animal character in the show. It's possible that more of his kind may appear in the future, especially considering Lammy's possible schizophrenia.