Nothing much is known about Tinklebell, as he does not play an important role in the series outside of a one time joke.
Like all fairies, he has Wings and a Crown but he wears a white cap and has a flashlight for his Wand. He wears a pink ballerina dress and a pink bow tie.
During the episode "Tiny Timmy!" Cosmo and Wanda were accidentally eaten by Vicky and ended up in "Kidney Land" inside her body. There they met Walt Kidney and his assistant, Tinklebell. Cosmo and Wanda knew him, but Tinklebell insisted to them that it was just a summer job, and asked for them not to tell his parents. He did not appear again in the series.
His name is a spoof of Tinkerbell, a Walt Disney character from Peter Pan and in the Tinkerbell movies who is voiced by Mae Whitman.