Playing Nice for Now

Two guys or groups are at each other's throats. The Hero versus The Villains, the Jets versus the Sharks, the vampires versus the werewolves... you know the drill. But then the cops or muggles or whatever show up, and bam! Time to put up the friendly faces and play nice with each other. The enemies instantly turn into best friends. And it will last until those nosy people have left the scene. maybe even a few seconds longer. Then it's back to trying to kill each other again.

Unlike Enemy Mine, the enemies are not teaming up against a mutual enemy, they are merely putting up a little charade to give an impression that they are not hostile to each other.

See also The Masquerade and Living with the Villain. Compare Teeth-Clenched Teamwork which happens when they're forced to play nice and work on the same thing.

Anime and Manga

 * There's a Crowning Moment of Funny for this trope in the Hellsing manga and OVA (Original Video Animation), where a meeting between Hellsing and the Catholics goes badly and Alucard and Anderson are about to throw down in an art museum, so Seras defuses the situation by pretending to be a guide and leading a group of elderly tourists into the room.
 * Natsu and Gray from Fairy Tail are always fighting, but will immediately put on huge smiles (and a cold sweat) whenever Erza Scarlett walks in.

Comic Books

 * In the Jean Valhardi adventure Le Soleil Noir, the eponymous hero makes use of such a situation to escape.

Film

 * In West Side Story, we have the Jets and Sharks putting up a facade for the cops. The cop doesn't buy it, but lack any evidence to arrest them for assaulting each other.
 * This occurs in Kill Bill Volume 1. The Bride and Vernita Green are fighting, but they temporarily stop when Vernita's four year old daughter Nikki arrives home from school.
 * Back to The Future. Marty and Biff do this when Strickland shows up.

Live Action TV

 * In Dexter season 5, Dexter drugs a villain, but the guy gets him with his tranquilized dart as he falls down. They both fall unconscious, and wake up in the same ambulance - quickly starting a friendly bickering about the "accident".
 * Seen in The Sarah Connor Chronicles episode "The Tower Is Tall But The Fall Is Short". Cameron and another Terminator have a Fight Scene that turns into an Elevator Action Sequence, and then into an Uncomfortable Elevator Moment when the elevator stops for a family of civilians. The two Terminators stand there silently for the duration, covering up their wounds, and then go back to beating the slag out of each other once they're alone again.

Western Animation

 * In the first episode of Wing Commander Academy, Maniac and Blair get into a heated argument. Maniac is about to strike Blair when Archer restrains him (using the Standard Female Grab Area no less) and then tosses him over her shoulder. Commodore Tolwyn and the Academy's commandant happen to witness that last part. The cadets claim that they were practicing for an unarmed combat class. Not quite an Enemy Mine take on the trope though, since Maniac, Archer, and Maverick are all comrades in arms (with a strong rivalry between Maniac and Blair, and a not inconsiderable amount of Foe Yay between Maniac and Archer.)