Conversation so far:
How did Kevin Clash's career get started?
Kevin Clash started working at Sesame Street for ten episodes in 1983, mostly performing nondescript, stand-in puppets known as Anything Muppets.
What projects did Kevin Clash do with Sesame Street?
Some of Kevin Clash's earliest characters on Sesame Street included the saxophone-playing Hoots the Owl, the infant Baby Natasha, and inventor Dr. Nobel Price.
What were Kevin Clash's characters on Sesame Street?
After 1985, Elmo, a furry red monster, became Kevin Clash's main character on Sesame Street.

Question: Did he decide on the characters or did someone decide them for him?
Self-contained rewrite: Did Kevin Clash decide on the characters he played in Sesame Street or did someone decide them for him?