Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Tearjerker: Dexters Laboratory
The wacky and fun episode of Dexter having to deal with Deedee's imaginary friend hanging out with him ends with Dexter wishing away the imaginary friend, and commanding him to never come back again. And he does. Deedee runs away sobbing. Then it fades to credits.