Continuity: In the episode 'Yesterday's Enterprise' (season three, episode 15), watch the final scene with Geordi and Guinan in Ten-Forward. Although time and the universe has returned to normal, Geordi is still wearing the uniform from the alternate timeline (note the sleeve detail, and the extended neck piece).

Revealing: When Tasha Yar and company first enter Ten Forward in the alternate timeline, watch through the doors as they open. An extra can be seen stood still in midstride in the passageway, before nervously noticing that the doors have already opened and that she has missed her cue to begin walking past. She then begins purposefully marching down the passage.