Bird Dancers

From Muppet Wiki

A group of Bird Dancers could be seen in several episodes of The Muppet Show. Performed by dancers from London's Royal Ballet, they wore a full head-covering, Muppet-like mask and human dancer costumes, making them look distinct from other full bodied dancers which were otherwise Muppet monsters.

They took the stage during Liberace's concert for birds in episode 309 and danced in the background for Chopin's Nocturne.

They also appear in episode 302 with Leo Sayer for the number, "You Make Me Feel Like Dancing."

In episode 421, they assist Doug Henning with a magic act. The female dancer is locked away in a wooden chest and switches places with Henning from behind a drop. She is carried offstage by an enamoured Doglion.