Karen Prell

Prell was born on July 26, 1959, in Florida but grew up in Seattle, Washington. She also performed some characters in other Jim Henson films and has enjoyed a significant second career as a computer animator for such studios as Pixar and DNA. On Sesame Street, she performed Deena Monster, as well as several background and one-off characters. She performed on the show from 1980 to 1981 for seasons 11 and 12, then returned in 2019 for season 50. She also performed in the 2003 attraction Sesame Street 4-D Movie Magic. Her website includes notes about working with Jim Henson and pictures of her custom puppets.

She puppeteered the Worm in Henson's 1986 film Labyrinth.

Prell started a "second career" when she joined Pixar in 1997. Here, she was an animator for Geri's Game and worked on animation of A Bug's Life and Toy Story 2.

In 2007, Prell began working for Valve Corporation, despite having no history of playing video games. She began this "third career" as an animator and playtester for Left 4 Dead 2, and followed this by doing concept work and animation for the Team Fortress 2 "Meet the Team" shorts. Her most notable character work for Valve was on Wheatley in Portal 2, which was influenced by her hand puppet work and involved "creating an extensive and intricately planned library of reusable movement and acting components that could be rapidly composited together to create unique actions for each of his hundreds of lines of dialogue." In a career retrospective, PC Gamer stated that "Prell did the impossible: She bestowed life on an orb."

Outside of her screen work, Prell has made public appearances performing Red Fraggle, like appearances at Comic Con. At Dragon Con 2013, Karen Prell was joined by fellow puppeteer Kathryn Mullen as part of the 30th Anniversary of Fraggle Rock where they performed their respective characters. She returned to perform Red Fraggle again for the 2020 Apple TV+ reboot Fraggle Rock: Rock On!, and the series reboot Fraggle Rock: Back to the Rock, of which she is also co-executive producer.

Prell married fellow Muppet performer Mike Quinn. They lived for a decade in England before moving to California to work for Pixar. Since divorcing in 2004, Prell and Quinn have continued to work together on different projects, usually involving the Muppets.