Comic Relief is a charity that helps raise money for the poor. Every odd-numbered year in March, people in the UK celebrate Red Nose Day. This is a semi-holiday created by Comic Relief where people get a foam red nose in exchange for a donation. Most donations occur during the live telethon, which is famous for its hilarious comedy sketches.
Naturally, most people anticipated a Doctor Who sketch because it is pretty much a telethon staple. In 2011, Rowan Atkinson poked fun at classic Doctor Who in this clip.