The Porcupine

From Muppet Wiki

The Porcupine is a character seen in Billy Bunny's Animal Songs. The puppet was later used in the chorus of The Muppet Christmas Carol and Muppet Treasure Island.

Official bio

from a 1993 press release
"The Porcupine that Billy meets along the way has a terrific singing voice and she also plays the saxophone. Her parents wanted her to be an accountant, but she resisted for the lure of show business and her dream of becoming the most famous singing porcupine in the world. She displays a sharp sense of humor and always gets to the point."