According to research online the following worked at Disney:
---Michelle Pfeiffer performed in DL Main Street Electrical Parade;
---Robin Williams was DL Jungle Cruise Skipper (such perfect casting!);
---Steve Martin at DL selling guidebooks and twirled souvenir lassos before becoming a magician at the Magic Shop;
---Kevin Costner worked as a DL Jungle Cruise Skipper (where he met and married Cindy Silva who was a character actress);
---Richard Carpenter of the Carpenters played the piano on Main Street at DL;
---Wayne Brady worked at WDW as a character performer;
---Kevin Richardson (Backstreet Boys) was a WDW character performer and backstage tour guide; once played Aladdin and TMNT at DL;
[Source w/pictures:
https://www.disneyfoodblog.com/2020...ore-they-were-famous-heres-where-they-worked/]
Found elsewhere on the 'net:
---Kathryn Joosten (Desperate Housewives) worked at MGM Studios now Hollywood Studios as a street performer;
---Joanna Kerns worked as an actress and took on the role of the Blue Fairy in the Main Street Electrical Parade;
---Ronald Reagan welcomed guests on the opening day at DL;
---Alyson Reed before being on the Disney Channel original High School Musical played Alice in Wonderland at DL;
---Terri Garr played the Statue of Liberty in Disney's Summer Spectacular Show in 1970 and at DL as a dancer in the parades;
---Colleen Ballinger (from Miranda Sings) was a performer at DL in the "High School Musical" parade and Playhouse Disney show;
---Taboo of Black Eyed Peas was a DL janitor before becoming a rapper;
---Sarah Butler of "I Want to Spit on Your Grave" fame and CSI Miami played Belle at DL;
---Leanza Cornett (Miss America 1993) in 1991 was the first actress to play the Little Mermaid at WDW;
---Ron Ziegler (Nixon's White House Press Secretary) worked as a DL Jungle Cruise skipper;
---Alexis Mateo (a RuPaul's Drag Race contestant) worked at WDW for 5 years as a character and dancer;
---John McEuen (Nitty Gritty Dirt Band) worked at DL at the same time as Steve Martin;
---Kara Monaco was Alice, Ariel, Cinderella and Snow White at WDW before becoming a Playboy Playmate;
Elsewhere:
---Taye Diggs worked at Tokyo DL
---Jennifer Hudson performed on the
DCL
I'm sure there are more!