Peter Davison and Bernard Cribbins are among the special guests who will feature on Doctor Who Live: The Next Doctor tonight (August 4) on BBC One at 7pm.
The special show will reveal the identity of the 12th Doctor, with host Zoe Ball interviewing the new Time Lord.
Davison and Cribbins, who played the Fifth Doctor and Wilfred Mott respectively, will be joined by a host of familiar faces including Daniel Roche, Rufus Hound and Liza Tarbuck.
Fans can also watch pre-recorded messages from the likes of Bruno Tonioli, Katy Manning, Anneke Wills, Janet Fielding and Bonnie Langford.
Current Doctor Matt Smith will depart the show in this year's Christmas special.