Who lives upstairs from Felix Unger and Oscar Madison in Neil Simon's the odd couple?

In Neil Simon's "The Odd Couple," the character who lives upstairs from Felix Unger and Oscar Madison is a woman named Muriel. She is Felix's ex-wife, and her presence adds to the tension in the story, particularly concerning Felix's emotional state and his past relationship. The dynamic between the characters contributes to the comedic and poignant moments of the play.