The cast of the sitcom, which ran for 200 episodes between 1998 and 2006, will meet again for the network's milestone celebration later this month.
Comedian brothers Keenen Ivory Wayans, Marlon Wayans and Shawn Wayans will also make an appearance to reminisce about about their '90s sketch show In Living Colour.
Other guests include American Idol stars Jennifer Lopez, Ryan Seacrest, Steven Tyler and Randy Jackson, 24's Kiefer Sutherland and Family Guy creator Seth MacFarlane.
David Duchovny, Gillian Anderson, Christina Applegate, Ed O'Neill, Katey Sagal, Calista Flockheart, Shannen Doherty and Jason Priestley are among the personalities already confirmed for the event.
The Fox 25th Anniversary special airs Sunday, April 22 at 8/10 ET/PT.
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Watch a clip from That '70s Show below: