What was the name of the puppet who lived in the Museum-Go-Round?

The puppet who lived in the Museum-Go-Round was Lady Elaine Fairchilde.

Lady Elaine Fairchilde was one of the central puppet residents of the Neighborhood of Make-Believe in Mister Rogers' Neighborhood. She lived and worked in the Museum-Go-Round, a whimsical museum that served as her home and workplace. Fred Rogers performed the character in the original series.

Lady Elaine was energetic, inventive, and mischievous, and she often used her mechanically powered “boomerang” to travel around the neighborhood. Her personality could be disruptive, but she was also creative and capable of helping solve problems. The character's unusual name and bold behavior made her easy to distinguish from the gentler residents of the neighborhood.

The Museum-Go-Round is sometimes confused with the homes of other major puppets. Henrietta Pussycat lived in the Rockit House, while X the Owl lived in an old oak tree. Queen Sara Saturday belonged to the royal family, and Lady Aberlin was another resident, but neither was the Museum-Go-Round's resident character.