 They had a series of guest hosts, maybe a dozen or more. You had LeVar Burton, Aaron Rodgers, George Stephanopoulos, Katie Couric, that guy Mike Richards, a whole bunch of others. Ultimately, they settled on two hosts, and they would do alternating weeks, Mayim Bialik and Ken Jennings. Mayim Bialik ends up leaving. Now it's just Ken Jennings.