- Main article: Sheldon S. Stickly
Sheldon (voiced by Anthony Capodieci) is a normal stick figure. He enjoys TV, magazines, and reading. He is always annoyed by Mr. Randoms. He first appeared in BIRTHDAY.
- Main article: Mr. Randoms
Mr. Randoms (voiced by Anthony Capodieci) is an insane stick figure with a huge, living bucktooth. It is possible that his bucktooth is inspired by the TeenChat Flipnote character Kimi's tooth.
- Main article: Tooth
Tooth (voiced by Anthony Capodieci) is Mr. Randoms' speaking, living bucktooth. He first appeared along with Mr. Randoms in Birthday and first spoke in Sheldon is 2012?!?
A random face with evil laugh (voiced by Anthony Capodieci), first appearing in Sheldon Balloon.
- Sun (voiced by Anthony Capodieci) is a star that orbits Earth.
- Earth (voiced by Anthony Capodieci) is the characters' home planet.
- Moon (voiced by Anthony Capodieci) is Earth's moon, first appearing in Cheese Magnet.
- Main article: Anthony (character)
- Anthony (voiced by himself) is the creator of the show. He commonly appears on the cover of Sheldon's books. He first appeared in Invisible Wall (on a book cover) and as an animate character in We Have Great Hair!
- TV (voiced by Anthony Capodieci) is a talking television set first appearing in Is That Too Much To Ask For?!
- The TV remote (voiced by Anthony Capodieci) is a television "clicker" first appearing in Lots'a TV!
- The Easter Bunny (voiced by Anthony Capodieci) is a holiday character debuting in Lots'a TV!
- Business Guy (voiced by Anthony Capodieci and formerly known as Random Businessman) is a businessman that first appeared in one of Anthony's updates where he stated he was looking for a job. He appeared again in Anthony's flipnotes "How Will My Job Go", and randomly appears in the newer Sheldon & Mr. Randoms episodes (first in That Random Gumball).