Both my boys started saying "What the heck?" out of the blue. This isn't a phrase I use nor do I think it's appropriate for 3 year olds to utter. It's such a habit they say it without realizing it until it's out. My typical response is the stink eye, a reminder that it's not appropriate, and a thinly veiled threat. It continues to happen. Next time I hear it I'm literally washing the perps mouth out with soap. *sigh* Grrgh! What the... ?!