Stiles was the most iconic performer on the original UK version of "Whose Line?", appearing in 76 of the series 136 episodes (including compilations). He first appeared in the fifth episode of the second season, which aired in late 1988. He appeared in one other episode of that season, before returning for four episodes of the third season. His prominence increased with each season, including appearances in every episode of Season 4 which was filmed in New York; ultimately appearing in every episode from the seventh season onwards.