juice box

last night caleb shows kevin and i a couple of tinker toys that have this black "gunk" on them. we ask him what that gunk is, but he doesn't know. so we ask him where he found those tinker toys, and he says in the seat of his desk. so kevin opens up the lid of his desk seat and it's filled with black gunk. just as i ask again what that gunk is, ethan walks in and says "juice box". so we ask ethan if he squirted juice box in there, "no" he says...