This's a sound effect designed by (and exclusive to) Joel Valentine, founder of Twenty-First Century Entertainment (AKA 21st Century Sound Design Corporation). It is NOT to be confused with a very similar sound, Sound Ideas, CARTOON, RATTLE - RATTLING, WOOD. The sound is probably made by a castanet, like most teeth chatter sounds are in cartoons.
- 2 Stupid Dogs/Super Secret Secret Squirrel (in "2 Stupid Dogs" segments only.)
- Chowder (Heard only in "The Froggy Apple Crumple Thumpkin".)
- Dexter's Laboratory (Twenty-First Century Entertainment episods only.)
- Foster's Home for Imaginary Friends
- The Fairly OddParents (Heard in "Fairly OddBaby" or confused with Sound Ideas, CARTOON, RATTLE - RATTLING, WOOD?)
- My Life as a Teenage Robot?
- The Powerpuff Girls (Seasons 1-6 only.)
- Samurai Jack (Seasons 1-4 only.)
- Wander Over Yonder (season 2 only)
- What a Cartoon (21st Century Sound Design Corp. episodes only.)
- Periwinkle Around The World (Shorts)
- Welcome to Wackamo (2006 Cartoon Network Pilot)
- Foster's Home for Imaginary Friends: Cheese Quest Music Video