Boy, where to start? My three or four year old son wandering around our one year old and supposedly childproofed house, found a bottle of tire shine and decided it looked like water. Luckily, it tasted like crap and he spat it all over the carpet.
My three year old daughter in response to my five year old son constantly blowing the whistle on the train under the Christmas tree "I hate that flargging thing!"
One night I was slightly drunk and changing in front of my daughter, we don't stress hiding the body in this house, not nudists but you know. She pointed at the package and asked what's that. I thought she wasn't listening, I thought she would never remember when I said "Mommy's lollipop". Three weeks later, mommy and her were in the laundry room while I shed my work clothes, my daughter pointed at my junk and said "lollipop!". Yeah explain that one to the wife.
My boy, now 12, has taken to saying "mother beeper" as opposed to dad's version. One day he was playing some Xbox shot crap game and I happened to be close to the stairs. I heard the real deal, full daddy, worked in a steel mill for 21 years, curse like a sailor language out of his mouth. I shot down the stairs, grabbed him by the shirt and pulled him into the service room. I told him EXACTLY what would happen if I ever heard those words out of his mouth in my home again. Then I reminded him what his mother and grandmother would do... have never heard a curse since.