Johnny
Played by Tommy Wiseau, Johnny is a successful banker from San Francisco who is engaged to Lisa. His characterization throughout the film is rather murky. However, it is evidently clear that Johnny is an eccentric, energetic, and jealous man who is a part of love triangle with Johnny, Lisa, and Mark.
Much of Johnny's dialogue have become well-known by households across the world (lines like "Oh hi Mark" and "You are tearing me apart Lisa.") And it is mainly because of Johnny that the film is as bad and as funny as it is.
Lisa
Lisa is Johnny's fiancé - apparently. However, she also loves Mark, thus creating a love triangle between herself, Mark, and Johnny. Although she is headstrong, intelligent, and beautiful, Lisa is also frequently unfaithful and is often annoying to many of the characters in the film.
Mark
Mark is the third person in the love triangle. He is having an affair with Lisa (Johnny's fiancé) and is an untrustworthy, rude, and somewhat petty person who, despite being friends with Johnny, doesn't care if he hurts him.
