I'm assuming the train that some airports have that takes you from concourse to concourse doesn't count?

The only real train I've ever been on was an Amtrak ride from Los Angeles to Sacramento when I was four years old. I remember eating pizza on the train and thinking it was amazing and the lady who served it to me mentioning Ninja Turtles and how much they like pizza, and then asking me if I liked Ninja Turtles, because her kids liked Ninja Turtles, and I was like "OMG YEAH NINJA TURTLES ARE TOTALLY RADICAL I LOVE THEM THEY'RE DA BOMB!" The concept of being served a meal inside a moving vehicle was mesmerizing to 4 year old me for some reason.

Then I remember asking my mother why there was a thin sheet of paper going down the back of the seat, and she told me it was so that the oil from people's heads wouldn't get all over the seat, and I didn't get it back then. Speaking of which, I never see that anymore.