This sound editing company, Twenty-First Century Entertainment (formerly known as 21st Century Sound Design Corp.) was founded by Joel Valentine, and has worked on the following shows, movies and TV specials, mainly ones from Hanna-Barbera and Cartoon Network. They usually credit sound editing only.
- 2 Stupid Dogs/Super Secret Secret Squirrel (2 Stupid Dogs segments only)
- The Halloween Tree (1993)
- The Town Santa Forgot (1993)
- What a Cartoon (many episodes) - Audio Services, Sound Editing
- Dexter's Laboratory (first two seasons only)
- The Powerpuff Girls
- Samurai Jack (Seasons 1-4; Joel does work on Season 5 though)
- The Powerpuff Girls Movie (2002) - Sound Editorial and Design
- Foster's Home for Imaginary Friends
- The Powerpuff Girls Rule! (2008)
- Korgoth of Barbaria
- Sym-Bionic Titan