Do you have a child that is a know-it-all?
I have one. Actually, I have several, but fortunately they take turns between being THE most annoying know-it-all, and being the one who has to have the last word. In which case you don't really have to know it all, you just have to be the loudest.
Here's the scene, twelve cars deep in carpool, people behind us, running late.
Child 1: I can't get the door open!
K-I-A: Unlock it!
Child 1: It's unlocked already!
[Sound of screeching plastic while handle is pulled five hundred times. Meanwhile, more cars piling up behind.]
K-I-A: [Reaching OVER Child 1 to make sure the door really IS unlocked, because one can never be too sure of another's ability to unlock a car door.] There must be something wrong with the door!
Mom: Child 1, please don't break the door handle. K-I-A, would you please go out and open the door from the outside for Child 1?
K-I-A: No, that won't work. There's something wrong with the door!
Child 2: I bet it's the child safety lock.
Mom: Yeah, I bet it IS the child safety lock.
K-I-A: [Scoffingly] We don't have child safety locks! There's something wrong with the door! Hurry! There are people behind us!
Mom: Here. I can pull up and a teacher will open the door.
[Teacher opens door easily from the outside. Child 1 gets out. Mom pulls away from curb.]
K-I-A: Man, I wonder what was wrong with the door?
I give up.