Seth Snella is a baby and supporting character in the series who appears in The Last Straw. The Snellas throws a half-birthday for Seth, and make the adult guests do crazy things to try and make him laugh. Mr. Snella tapes all the adults and then send the videos to "America's Funniest Families".
- Diary of a Wimpy Kid: The Last Straw (First appearance)
- Diary of a Wimpy Kid Online (As Seth Smedley)