Superficially, this film belongs roughly in the same genre as "All of Me" and "Liar Liar," comedies in which a character becomes the victim of some weird supernatural fate and must adapt to the insane logic of the situation. But Steve Martin and Jim Carrey are geniuses of physical comedy, whereas Bill Murray specializes in understatement. I can't imagine any other approach having worked for this film, where the world is going crazy around Phil the weatherman, Murray's hard-edged character who keeps his emotions bottled up. What makes the initial scenes in which he first discovers his fate so hilarious is the mounting panic in his demeanor even as he tries to act like everything's normal. All he can think of to say is, "I may be having a problem." Uh, no kidding. Throughout the rest of the film, he'll deliver similarly muted lines to describe his situation, like "My years are not advancing as fast as you might think." It's striking that a man who has all the time in the world would choose his words so carefully, but it reflects a well-conceived screenplay.
In this comedy, the laughs are reinforced by repetition. The absurdity of Phil discovering that he's repeating the same day is funny enough, but every time that alarm clock goes off, and the radio starts playing, "I Got You Babe," and Phil goes through the same motions and meets the same people and then goes out into the street to be accosted by the same annoying high school buddy ("Phiiiil?"), I laugh again because I'm reminded how funny it was the first time around. People who didn't like this film (I've met one or two) emphasize how annoying it is that everything gets repeated. I sort of understand that complaint, since jokes repeated over and over usually fail miserably. "Groundhog Day," however, works uniquely well because the situation gets increasingly absurd and Phil gets increasingly desperate with each day that fails to pass.
The film would have fizzled out quickly had it spent the entire hour-and-a-half showing Phil meeting the same people and doing the same things time and again. The fact that "Groundhog Day" avoids this fate is one of its more striking qualities, since most high-concept comedies of this sort fall apart in the third act. "Groundhog Day" is a rare example of one that completely follows through with its premise, leading from the initial situation logically to the ending. Only the Jeopardy scene feels like a skit that could have appeared anywhere. But this scene actually is placed wisely: it occurs when Phil is becoming increasingly bored and lethargic, and it is used to separate two hilarious scenes where he gives nutty television reports.
It is in the middle, centering on Phil's attempts to seduce Rita, when the film reveals itself to be more than just a comedy. The underlying implication of these scenes is that Phil's powers are less important than he thinks they are. He probably could have done the same things (such as his exploits with Nancy) under ordinary circumstances, without the hocus pocus. In the end, his powers don't matter, because Rita is too smart and sees right through him. She may not understand the full supernatural implications of what he's doing, but she senses that he's somehow manipulating the situation. Phil may think he's a god, but he isn't all-powerful.
Phil's character development is convincing largely because we can so easily believe the situation would force him to look inward. Because he loves such a sincere woman as Rita, the only way he can finally impress her is by genuinely changing himself rather than faking it. The change he undergoes isn't an implausible leap, for he maintains many of the same basic character traits he had at the beginning, even though he becomes kinder and more caring. Earlier, Rita says that egocentrism is Phil's "defining characteristic," and, indeed, he doesn't stop being egocentric at the end; he merely learns to channel the egocentrism in a positive direction.
I have trouble imagining any other actor having pulled this off. Murray is not the only comic actor to have proved himself capable of dramatic depth, but he's one of the few who can so seamlessly combine his humorous and serious side into the same character. And he's a master at conveying complex emotions through an apparent deadpan. When his delivery sounds stilted in this film, the effect is intentional, for he's playing a man whose life has become a script.
Though this film has a serious message, it is still quintessentially a comedy. But it's a comedy that uses psychological exploration of a fascinating character to make its point. After the laughter has worn down, "Groundhog Day" turns out to be one of the richest and deepest films I've ever seen.