Not one story - a couple stories and observations about hellspawn.
1. Grabbies. Kid with family wandering the mall... kid howls "Nintendooooo!" and runs into the store, grabs a game box (empty display) and runs out into the mall to show mom and dad. Mom and dad don't seem to mind too much that little Billie potentially just shoplifted and dont' seem out-of-sorts at all when annoyed me tromps after them and manhandles the game (box) out of Billie's hand and return it to the store. Doesn't this seem like an object lesson for the little klepto-in-training? Never seemed like it.
2. Climbers. Kids want something out of reach? Kid climbs. My store's shelves, however, were not exactly what you might call "bolted down". They slid into and out of position easily (and were about a foot deep - natural climbing platforms). Anyhow, when the little monkeys started climbing, I'd rush in, quickly put my hand on the shelf to keep it from coming off, and pulled the kid off. And sometimes tell the parent not to let them climb since the shelves would collapse (which didn't seem to impress the parent). Occasionally the shelf would fall (either a loud crash that brought the employees running or just five seconds away from my outstretched hand) and the parent would become all doting and lovey-dovey over the now-crying kid, surrounded by a pile of game boxes. Somehow, they never got a head wound or broke something they might need later. And somehow the store (as far as I know) never got sued.
3. Misplacers. Yeah, kids don't put things back where they go (I'll alert the media). But adults do too. But what drove me nuts were the parents with the kids who were actively teaching them life lessons about not giving a crap about organization and the fact that employee would have to reshelf things properly. I had a manager who would follow these types around and, when they put something down in the wrong spot, he'd immediately snatch it up (in front of them) and put it in the right spot. He said it didn't impress the customers - they just kept doing it.
4. Unimpressed by Shrinkwrap - we weren't a bookstore but we did carry a small selection of hint guides for games. Corporate had us shink-wrap them to keep people from using us as an early version of GameFAQS. This wouldn't impress the kids (usually teens) who would pull the wrap off and start reading the strategies for Super Mario Whatever. This I usually ignored as something that ultimately wasn't harmful... until they are reading 10 minutes later or bending the cover or whatever. At which point, yep, I'd stomp over and take the book out of their hands and they'd get all upset.
5. The Man Behind the Curtain? Happily, our stores didn't have any actual gameplay stations or I'm sure we'd become the local arcade (as I gather happens at Gamestops these days). However, our store did have a couple tv displays running a loop of video from the current games. The footage was on VHS, inserted into a VCR (with bad tracking), and connected to the TVs which were embedded in a locked display box. Invariably a kid would watch the tv for a bit and go around behind the box and try to get the door open (usually locked but eventually the lock broke and they'd wind up starting at a VCR, a little confused). My question was always... what is your gameplan if you DID find a SNES or Playstation in that box? Were they prepared for their life of crime at that moment? Were they really going to steal the game or the system and go on the lamb?
Anyhow, none of this is Earth-shattering - just common occurrences that managed to repeat over and over again. Imagine that, working retail was like Groundhog Day....