- Main article: Sheldon S. Stickly
Sheldon 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 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 is Mr. Randoms' speaking, living bucktooth. He first appeared along with Mr. Randoms in Birthday and first spoke in Sheldon is 2012?!?
- Main article: Scary Face
A random face, first appearing in Sheldon Balloon.
- Sun is a star that orbits Earth.
- Earth is the characters' home planet.
- Moon is Earth's moon, first appearing in Cheese Magnet.
- Anthony 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 is a talking television set first appearing in Is That Too Much To Ask For?!
- The TV remote is a television "clicker" first appearing in Lots'a TV!
- The Easter Bunny is a holiday character debuting in Lots'a TV!
- Business Guy (formerly 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).