I’m going insane about this one:  So there’s a woman on a train and there’s a man seeing her off, and he’s in love with her but it’s not reciprocated.  As the train starts to fire up she sees him standing there sad on the platform and she yells to him to wave (Like “come on, wave”), but over the sound of the train he hears “wait” and perks up.  He then starts waving and chasing the train down the platform yelling that he’ll wait for her.

I thought it was possibly an old episode of cheers but I haven’t been able to find it.  Halp.