As an improvisational comedy show, Whose Line Is It Anyway is a series that relies upon the strength of its cast, as well as the energy of its audience. But in addition to these key components of any form of live comedy, the series also frequently features guest stars from different worlds of entertainment, including music, film, and sports.
While the original series didn't feature these guest stars quite as frequently, the revival series airing on The CW frequently features guest stars from the network's other shows as well as other works. It's clear that some celebrities just aren't quite cut out for the world of improv, but in the series' lengthy run, there are a few guests who clearly stand out among the rest.
Kunal Nayyar
Though most of his tenure as Raj on The Big Bang Theory finds Kunal Nayyar playing a more subdued nerdy character, Nayyar is able to totally let loose and show another side of himself in the series' tenth season.
When he takes part in a hard rock Duet with Brad Sherwood and Wayne Brady, Nayyar totally gets caught up in the music. And though he takes on a nerdy persona in a round of Helping Hands, the hijinks of cast members Ryan Stiles and Colin Mochrie allow him to get a little wild, too.
Alfonso Ribeiro
Best known for his iconic role as Carlton Banks in the beloved sitcom The Fresh Prince of Bel-Air, Alfonso Ribeiro more than shows his improv comedy skills in his appearance in the series' 12th season premiere.
Ribeiro appears in three different skits in his episode: Duet, where he is serenaded by Wayne Brady and Gary Anthony Williams; Dubbing, where he plays a mad scientist's assistant; and Living Scenery, where he plays the role of a prop. And of course, in the closing credits, he teaches the cast to dance "The Carlton."
Cedric the Entertainer
Yet another gifted comedic performer who steals the show is none other than stand-up comedian Cedric the Entertainer, who appears in the series' 11th and 16th seasons.
In his first appearance, Cedric gets really into a round of Questions with Hats, involving a dramatic high school reunion. But it's his second appearance that really stands out, where he joins Wayne Brady and Gary Anthony Williams in a Jamaican dancehall music performance of a song about an insurance adjuster.
Joey Fatone
It's not just comedians who can keep up with the live, unscripted atmosphere that Whose Line provides. Joey Fatone, formerly of the boy band NSYNC, appears in the eighth episode of Season 12 and delivers some of the series' most committed physical comedy to date.
Many of the sketches Fatone takes part in allow him to make light of his old boy band days. In Duet, he joins Wayne Brady and Jeff Davis in an NSYNC-style performance. But it's in Dubbing, where he gets to engage in a sexiness fight with Wayne's Justin Timberlake, that Fatone truly steals the show.
Sid Caesar
In the fourth season of the series' original run, Whose Line presented a "Salute to American Television," featuring the legendary Sid Caesar. Caesar only appears in one sketch in the episode, but he receives a hero's welcome upon his arrival and a serenade of "Happy Birthday" with a cake at the episode's end.
In his single sketch, Caesar accompanies Drew Carey in a round of Foreign Film Dub, showing out his incredible range of dialect work and stealing the show in the process.
Florence Henderson
Florence Henderson might be one of the all time great television moms in her role as Carol Brady in The Brady Bunch, but Henderson's appearance on Whose Line is decidedly less family friendly.
Henderson first appears in a game of Duet with Wayne Brady and Brad Sherwood, where they serenade her in disco style and with very non-PG lyrics. Her misadventures continue in Dubbing, where she's portrayed as a desirable housewife torn between her husband and her pool boy, and in Helping Hands, where she aggressively berates Ryan Stiles' Jan Brady for her whiny behavior.
Stephen Colbert
Though best known for his work in late-night television these days, Stephen Colbert excelled in improvisational comedy of another kind in his two appearances on the original series as a guest panelist.
He gives an unexpectedly hilarious performance in an avalanche-themed game of Scene to Rap, and has all too much fun as an Overly Dramatic Shakespearean Actor in an uncensored cut scene of Let's Make a Date.
Wil Wheaton
Whether known best for his work in Star Trek, his role as Sheldon's nemesis in The Big Bang Theory, or for his all around online nerd cred, Wil Wheaton is a man who continues to surprise and entertain no matter where he is. Whose Line is just another such example.
Playing both entirely against type and in line with it, Wil joins Wayne Brady and Gary Anthony Williams in a boy band performance about Dungeons and Dragons that is one of the revival series' best music numbers to date.
Richard Simmons
If there's two things that shouldn't go together in any way, it's the world of Whose Line Is It Anyway and fitness and wellness guru Richard Simmons. But when Simmons appears on the improv comedy series, he truly turns in a performance that is one for the ages.
In fact, Simmons appears in almost every single sketch in the episode he appears in, and for good reason. Not only does he meet the performers mile for mile in terms of energy and enthusiasm, but the cast can barely keep it together, making the episode entirely hilarious from start to finish.
Robin Williams
It's not every day that Whose Line had a major celebrity among its guest cast, but all of that changed when Robin Williams appeared on the series in 2000. More high energy and more willing to go to crazy lengths than almost anyone else in the show's history, Williams makes this episode another of the franchise's greatest of all time.
Whether taking part in a hilarious round of Props with Wayne Brady; performing as a fashion police officer in Party Quirks; or joining Wayne in a gospel style Duet, Williams goes all in from start to finish, and brings the laughs every second he's on screen.