Your first thought of an antagonist might be of a “bad guy” or “villain.” Sure, an antagonist can be the so-called heavy in a film, but then not every film has a ner-do-well. Sometimes the antagonist isn’t a person at all, but rather an antagonistic force like a hurricane, an avalanche, a raging fire, or even an emotion such as fear or hatred. But then there are films that don’t seem to have either personified antagonists or antagonistic forces. In that case, established characters in the story may step into the antagonistic role, even if only for a scene or two.
Remember the movie Clueless? When Cher (Alicia Silverstone) needs a push to realize that she has romantic feelings for her former step-brother Josh (Paul Rudd), her protege Tai (Brittany Murphy) steps into the part of love rival. The only real purpose of an antagonist or antagonistic force is to push the protagonist forward. To push him into making decisions he wouldn’t ordinarily make, or to come to conclusions that might otherwise elude him.
If a film’s primary antagonistic force is too weak to push the protagonist, then other characters might be called on to act as antagonists even though they have the best of intentions toward the main character.
For instance, in 40 Year Old Virgin it was fear that was holding back Andy Stitzer (Steve Carrell.) That antagonistic force was a wall preventing him from moving forward in life. But walls don’t move, so Andy’s coworkers stepped into antagonist roles and tried to push him past his fear even though it caused him pain (the chest wax) and led to several small disasters that ultimately forced Andy to climb over that daunting wall himself.
The antagonist pushes until the protagonist finally pushes back.