The Seventh Doctor's New Digs

After spending a good chunk of the serial in his previous incarnation's patchwork outfit, the Seventh Doctor goes to a wardrobe to try on a variety of costumes for his potential new getup, including a few of his previous incarnations' outfits. After settling on one, the Doctor nearly realizes that "Mel" is actually the Rani in disguise before she slaps him (as seen from his point of view) to keep him from putting two and two together.

Example of:
Costume-Test Montage