That’s funny… Everyone I know calls them Underdogs, not underducks. Maybe it’s different in different places (I’m from Chicago) You push the person in the swing, then say One! (push), Two! (push), Three! (push)… Underdog! And you push hard and run under the swing. The 2 kids I babysit for are constantly asking for them. I usually say no, especially with the older one (longer legs), cause I don’t wanna get kicked in the back! It is fun to give, though!