Hobbit

My youngest child came home today smelling of urine. I had him change clothes and wash up, after which he returned and sat down beside me.

"Why did you wet your pants?" I asked, thinking there may have been a good reason.
"I don't know," he replied. "It's a hobby."
"A hobby!?" I said.
"Yeah. A bad hobby."
"You mean a habit?" I asked.
"Um, what's a hobby?" he replied.
"Something you do for fun in your spare time," I explained.
"Oh. It's a habit. A bad habit."