Most of us would have the same reaction if we saw Ben Stiller in this situation. I'd pobably react this way just seeing a gentelmen get up and give me his seat, in general.
In trying to relate to this story, the best one I have is when I was holding the door open for an older couple at a steakhouse in Los Angeles and Ashton Kutcher with Mila Kunis walked through the door as well. I about died. Well, inside. I was well put together on the outside until I immediately called my best friend and screamed, "GUESS WHO I JUST HELD THE DOOR OPEN FOR?!"
I only wish we could have seen this woman the minute after Ben left. I bet she was this exicted for an entire day.