When students walk in the door and see a substitute...all of the sudden, you have 20 children that have to use the bathroom at the same time.
I had a Spanish professor in college who told us that if she found papers with no names on them (believe it or not, this is a problem in college), she would throw them in her woodstove. We used to think she was kidding but it turns out, she was dead serious. Nothing like keeping your house warm with the handouts of no name students!
Everyone is missing a black mitten, but no one owns the one mitten I actually find. When trying to work out a problem between students they forget their role in the situation but clearly remember everything the other child did in detail. Most hitting, kicking, punching and otherwise physical behavior happens 'on accident'.
Definitely ice packs, band-aids, and the need to get a drink. I have a few kids in my class with a pretty bad cough. A few days ago I took a minute to talk to my class about coughing and sneezing into their arms to keep from spreading germs. Wouldn't you know it, within a matter of seconds a dozen more kids came down with a cough.