I give up.

"Mom, I'm 5," he says with a mischievous smile.
"No, you're 4. When will you be 5?"
"July 16."
"Would you like to have a ninja party?"
"No, a train party."
"What about a Dinosaur Train party!? Wouldn't that be fun?"
"How about a diesel train party? Or a speed train party?"

I give up. You can take the boy away from trains, but you can't take the trains out of the boy.