I joke that my children are auditioning to be Fonzie. No, they haven't seen Happy Days. It started with K. We'd sometimes say "hey" to him when he was being silly or getting into something, and he started repeating it. When he repeated it, though, he protracted it into a "heyyyyy". C started mimicking him, and sometimes I'll find her sitting in a room just saying "eyyyy" over and over. It's even funnier when they're both doing that at the same time. Now I just need to get them leather jackets and teach them to put their thumbs up when they say it.