The Stolen Mirth was a skit in The Muppets Take the O2 stage play. It was a crossover between The Muppets and Doctor Who, and, more specifically, part of the Muppets franchise's Pigs in Space series-in-a-series.
The 13 July performance was titled The Stolen Mirth and featured the Tenth Doctor while the 14 July performance was titled Mirthshock and featured the Fifth Doctor.