Shelby, as portrayed in Smallville.

Shelby is Jonathan, Martha and Clark Kent's Golden Retriever. He first appeared in the graphic novel Superman: For All Seasons and has subsequently been adapted for television in Smallville. The comic book version of Shelby is a Border Collie.

In modern-age comics continuity, he was one of (at least) two dogs belonging to Clark and the Kent family while Clark was growing up, the other being Rusty, a retriever. Krypto, the Superdog also belongs to Superman and was kept on the Kent farm in Pre-Crisis comics while Clark was growing up, and in fact Shelby in Smallville is often considered as an interpretation of Krypto, seeing as he had Super-Strength (but only in his first appearance).

In other media

History in Smallville

Before he was adopted by the Kents, he belonged to Zack and Josh Greenfield, who work at a veterinary clinic in Smallville. They called him Einstein, because they enhanced the dog's intelligence and strength with Kryptonite. Shelby ran away from them, and was hit by Lois Lane. She brought him to the Kent farm, where Clark discovered the dog's super-strength. Clark wanted to call him Krypto, because he was cryptic. When Jonathan agreed to keep the dog, Clark and Martha named him Shelby, after a dog that Martha once had as a child. Clark, in particular, felt it was a better name than what Lois had in mind: Clarkie.

When Dr. Hudson inhabited Clark's mind, Shelby's barking at John Jones helped Clark come out of the prolonged hallucination.

Shelby no longer has enhanced abilities because the serum that was used wears off after a few days. ("Smallville")

Shelby is portrayed by a Golden Retriever named Bud.

History in Lois Lane: Fallout

SmallvilleGuy has a dog named Shelby, who gets along with his farm's new-born cow, Nelly Bly. He showed his online friend Lois Lane a picture of the dog and calf. ("Lois Lane: Fallout")