Three-year-olds can be pretty darned fickle sometimes.

For months, my son Alex had been hinting he wanted to sleep in the “big boy bed” that sat in the corner of his room, on wall opposite his crib. My husband didn’t want to rush it. “He’s not ready yet,” he said, which to me was code for: we give him a free pass out of “crib” jail, and the next thing you know he’ll be opening doors and running around the house—and into our bed at 5 a.m.

I had a different take on this. As the “Mean Mommy of Milestones,” the parental unit that threw out Alex’s bottles soon after his first birthday, and tossed out the diapers just before his third, I felt it was high time this kid slept in a real bed.

My reasoning was it would encourage him to night train – to get out of bed in the morning and use the potty. Not only that, but the idea of him climbing in and out of a crib seemed much more dangerous than him climbing out his bed (which was much lower to the floor).

Encouraged by his interest in the big bed, I happily went ahead and ordered sheets, a blanket and pillowcase decorated with the Cars theme. If there was anyone who could get Alex to sleep in a big boy bed, it was Lightning McQueen.

I was wrong.

Read Ways to Bribe - Um Sorry, Reward - Your Kids

Shortly after tucking my son into his new bed, surrounded by his army of stuffed animals and toy cars — and Lightning, I shut out the light, thinking smugly of the delighted look on my son’s face as he curled up in his new bed. The Mean Mommy of milestones has prevailed again, I thought.

Less than five minutes later, we heard this tiny voice plead from the baby monitor: “I waaaaaaaaaant to sleeeeeeeeeeeep in my criiiiiiiiiiiiiiiib!”

Since then, my son has refused to sleep in his new bed; holding on to his crib as Linus does with his blanket.