Choo Choo! (Train pun)

Trains.
During my recent trip to Japan, my father commented on the amount of effort it must have taken to make a train pass a mountain.

Me:
It wouldn't be that bad if you were trained.

Father:
...

Me:
Actually, you are right. It would be a mountain of work. You've got me all railed up now.

Father:
. . .

Me:
I'm sorry for interrupting your train of thought, go ahead.

Father:
What have I done?

(Rating: 3.5/5)