When people talk about the longest-running TV shows in American history, will they remember to mention Whose Line Is It Anyway?

Before August 1998, improvisational comedy wasn’t even really seen on television. Certainly not as the main attraction. But on Aug. 5, 1998, Whose Line made the move from British telly (and Comedy Central) to American primetime. Drew Carey, star of ABC’s The Drew Carey Show, convinced the network to give it a try, especially since he’d host it and one of the regular improvisers was his sitcom co-star, Ryan Stiles. Two other regulars from the UK edition — Colin Mochrie and Wayne Brady — made up the main cast, with the fourth improviser chair open for a rotating guest comedian.

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Fun fact: Two weeks after Whose Line debuted on ABC in primetime, Comedy Central premiered the first episode of Upright Citizens Brigade.

Perhaps this month, 20 years ago, was either the birthplace of, or the ground zero (depending upon your opinion of improv!) of the improv comedy craze in America. Whose Line inspiring a generation of short-formers; the renegade UCB inspiring a generation of Del Close long-form Harold proteges.

Either way, improv comedy would never be quite the same.

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Whose Line superfan Angela from Greece also put together this collage of the most popular performers to appear on the show over the past 20 years.

They include the four mainstays from 1998, new host Aisha Tyler, who has more than 100 episodes under her belt on The CW, plus: