He actually dropped that poor child!
That was just a sound effect. I'm sure they didn't actually drop the child on the floor. Probably had a blow-up play thing underneath. The sound effect made it seem real. They also used sound effects for the spanking part and also when the baby fell over on the couch and bonked his head. The sound effects are part of what's so funny. Also, when the baby is laughing as it's being scolded and spanked, that's pretty hilarious.