A line used in kids' shows, sitcoms, and kids' sitcoms, at the beginning of the episode, just before Hilarity Ensues.
The characters will be discussing whatever the subject of the episode is and someone will say, "This is gonna be the best (whatever) EVER!"
Then, everything goes horribly wrong, but of course later they realize that it didn't go SO badly after all. "It really was the best (something) ever!"
Nickelodeon does it ALL THE TIME.