This is really tacky. A lovey dovey couple today walked into a crowded train together. They stood through two stops, until one seat in front of them vacated. Now, in a similar situation, my husband would likely ask me to sit while he stands next to me, and if I'm tired, I'll sit, but if not, I'll continue standing with him because it's easier to carry on our conversation.
But this couple, the guy sat down immediately, with the young woman whining that she wants to sit too but refuses to sit away from him. So, instead, he tells her to sit right ON TOP of him! So there they were, doubling up on each other on top of one seat. As the train moved, this "body tower" shifted from left to right, right to left to front, completely getting in the way of the passenger seated next to them. They then pretended they were on a roller coaster ride together. They were young, 20s maybe, but not young enough to act like idiots.
It was completely ridiculous and immature. They continued to sit on top of each other over one seat until the train emptied out at Embarcadero.