That sounds like it is funny

I only heard one side of the conversation, but according to Auntie, and from what I heard, it went something like this

"Hi!"
"Hi Gavin, whatcha doin?"
"I'm playing with my trains"
"Do they go 'Chuggggaaa chugggaaa chuggggaa chugggaaa CHOOOO CHOOOOO'?"
"That sounds like it is funny. BYE!"

He does tend to end his phone conversations on a whim...