Little kids logically will say keeped, sleeped, etc. My grandson is growing out of it now, but has been known to do so. Bill Bryson makes note of it in his excellent book, The Mother Tongue. (I think it's a little out of date, though, on some things. It was written in 1991 and fairly predicts the demise of Irish Celtic, etc. Wish he would do an updated version.) Still worth the read and done with much laughter pointing out absurdities, origins, etc. in a very entertaining way.