However , David Tennant appears as himself and John Barrowman is revealed as playing Captain Jack in the TARDIS set .
In the scene , Barrowman appears initially as Captain Jack confronting an alien on board the TARDIS who claims to be the Doctor .
David Tennant appears as himself and Barrowman   is revealed as playing Captain Jack in the TARDIS set .
In the scene , Barrowman appears initially as Captain Jack confronting an alien on board the TARDIS who claims to be the Doctor .