One or two actors can carry a comedic film so dominantly that that viewers forever associate them with those roles. These movies are character- and dialogue-driven. The humor comes from their interaction and their verbal volleys, or one-liners delivered from the lead character. Notable duos based on this element include Tommy Lee Jones and Will Smith in "Men in Black" and Billy Crystal and Meg Ryan in "When Harry Met Sally." Notable solo stars who mastered this element include Mae West and Woody Allen.
Gags can be either visual or verbal. Michael Richards, who played Cosmo Kramer on the television comedy "Seinfield," famously used this element in a visual sense, slipping, falling and using facial expressions. Verbal gags deliver through quick punch lines. Peter Sellers' Inspector Clouseau character in the "Pink Panther" movie series made good use of gag elements, as well as Mike Myers in the "Austin Powers" films.
Some comedy films drop an ensemble cast into impossible, ludicrous situations that carry the entire movie. In "Hangover," four men spent an intoxicated night in Las Vegas only to literally lose one of their members -- with no memory of where he might have gotten to. Their antics and trials in trying to find their lost pal carried the movie. In "Meet The Parents," Ben Stiller endured an entire weekend of bizarre disapproval at the hands of his future father-in-law, Robert De Niro. His hapless responses formed the basis for the movie.
The timing of gags and lines is another important element of comedy fare. These movies have a tempo that allows a brief lull after each prank, pratfall or comedic incident -- or series of them. This prevents the plot from moving on without the full attention of the audience who, hopefully, are all rolling in the aisles and not looking at the screen. Ideally, the uproar is such that no one would hear ongoing dialogue anyway. Think of Zach Galifianakis' character finding the tiger in the bathroom at the beginning of "Hangover." A mini-break followed as his Alan Garner character hastened to the suite to tell the others what he had found, then the plot moved on again.