I don't believe these riding styles are approved by the manufacturer

When we were at the store recently checking out their birthday bikes, the girls had a little trouble deciding. They zoomed all over the store, hopping on this bike and then that one, pedaling furiously up and down the aisles. (It was a little hairy, to tell the truth, I'm actually shocked that they didn't take out any innocent bystanders.) Anyhow, there were sporty orange and purple racing bikes, girly pinkety-pink bikes, rugged speed bikes with hand brakes, fendered bikes with tv characters, and even trick bikes—the extra sturdy kind with those sticky-outy pegs that you can stand on (I think they're called axle pegs, in case my description just doesn't do it for you). Anyhow, we know our girls, and we know the kinds of things they dream up. So we tried hard to push them toward the trick bikes. Yeah... no dice. They were just not interested, and we came home with some adorable, sweet, girly pink and purple bikes. But I suspect they were paying attention when we talked about what you could do with those trick bikes, because they promptly set about doing this kind of stuff: Hmm... Does anyone know if there's an after-market kit to add axle pegs and miscellaneous and sundry braces to normal bikes? Basically, a twin-proofing kit for bicycles?