David Tennant's 10th Doctor Who is to meet the fifth Doctor in a special episode for Children in Need.
The episode is called Time Crash, and will see Tennant team up with actor Peter Davison on 16 November.
The episode was written by Steven Moffatt, who's also written lots of the best episodes of the show since it was brought back to TV.
Davison said: "It is an honour to be able to make the connection between the Fifth Doctor and the 10th Doctor"
The Doctor will be back in 2008 for a fourth series of the show, with Catherine Tate returning as his assistant.