Mike Wazowski’s girlfriend in Monsters, Inc. is Celia, more fully known as Celia Mae. She works as a receptionist at the Monsters, Inc. factory and is played by Jennifer Tilly.
Celia is a pink, cyclops-like monster with purple snakes for hair and tentacle-like legs. Her relationship with Mike provides comic friction because Mike’s reckless involvement in Sulley’s efforts to hide Boo repeatedly puts Celia in an awkward position. She becomes especially angry after the child’s presence triggers a dangerous containment operation at Harryhausen’s restaurant.
Viewers sometimes choose Roz because Roz is a prominent female character at the factory, but Roz is actually the administrator of Scare Floor F. She is also secretly connected to the Child Detection Agency. Boo is the human girl Mike and Sulley are trying to protect, not Mike’s girlfriend.
By the end of the film, Celia and Mike reconcile. In Monsters at Work, she receives a promotion to floor supervisor after Mike and Sulley take charge of the company, extending her role beyond the original movie.