… you go swimming in the ocean and you hear an orchestra playing “bum-bum, bum-bum” at a quickening pace.
You answer the door and the guy on the other side introduces himself as “Lenny Briscoe”
…you’re at a computer conference demonstrating how easy the new Windows 98 is with Plug and Play, by hot-plugging in a scanner while your boss Bill Gates watches from behind you on the stage, and you get the Blue Screen of Death[sup]TM[/sup].
…Tippi Hedren develops a crush on you.
…you’re in a Disney movie and you have a child.
You’re a hefty fellow from New Orleans named John and you’re holding up the timbers in the bottom of a mine while twenty men scramble past you to safety.
… you walk into a quaint British hotel and see John Cleese behind the reception counter…
… you’ve decided to be nice and helpful to the Baudelaire orphans…
… you’re victory over the meddlesome human children is assured, because you just killed the obnoxious talking lion last night…
…you have to tell Tom Hagen to pass the word to Michael that it was only business, not personal.
… you hit “submit” instead of preview, just this once… ::sigh::
…you’re cousin oliver shows up.
That little Spanish brat shows up with a sword saying, “My name is Inigo Montoya…”
You think you have a nice long management career ahead of you and you get hired to manage the Chicago Cubs.
(Every Cubs manager since Lee Elia, after leaving the Cubs, has never managed again)
…The man you tortured will not chop your ears off…so you can hear children screaming about your face.
…your alter ego has your own gun in your mouth.
…I help the Professor and Skipper with the rescue.
You see your friend you thought you’d had murdered. And isn’t that your body lying in the pool of blood.
Couldn’t help myself. 
You are undermedicated and are coming out from anesthesia on the operating table,andyou hear either:
“OOPS!”
or:
“What do you mean this was the HERNIA, not the sex change patient?”
…Mike Hammer falls in love with you
…any of the Cartwrights fall in love with you.
…Captain Kirk falls in love with you.
…basically when any star of almost any action film or TV series falls in love with you.
That is just a gorgeous, gorgeous post. Cheers!!
…you suddenly realize you’re explaining your whole plan to the good guy.
…everyone but you suddenly stops making fun of the principal at the exact same moment.
…you’re the protagonist’s mentor and you realize the Act Two Reversal is due any minute.