If a kindergartner gets an apple for lunch, he/she will stab it with a fork and try to eat it like a lollipop.
They are always shocked to discover everyone in the class is five or six...In fact, I've had several say to me, "Hey! Guess what? I'm five and he's five, too!"
In kindergarten, the "S" word is stupid or shut up. They are quite scandalized when someone uses these words.
If someone is caught using the "S" word, he/she will often say, "I was just sayin' it to myself."
Very often, kindergarten children will rattle off a bunch of nonsense words and tell you they are "speaking Spanish." Many times they will do this to actual Spanish speakers who, oddly enough, seem unphased by this.
At nap time, if one of them starts coughing, they will ALL start fake coughing. Seriously, it's like working in a tuberculosis ward.
When they first begin to write their names, they will often write them on furniture. When caught, they will deny it, because they haven't figured out that they're the only ones who would write their own names.
Guest speakers who haven't spent a lot of time with five-year-olds will usually ask the kids, "Are there any questions?" Which ALWAYS elicits the response, "One time, I was at Chuck E. Cheese...." Suckeerrrs....
Every time an X-men movie comes out, I have to say, "Take your crayons out from between your fingers. You are not Wolverine."