As a parent, I have to say that's a legit fear.

Although the cover features the traditional try-outs and desk yes/no buttons, sadly there's no such scene in the issue: from 2008, Legion of Super-Heroes in the 31st Century #16, "The Untold Legend of Arm-Fall-Off Boy" Written by Matthew K. Manning, art by Shawn McManus.

In his first, and only prior appearance, Arm-Fall-Off Boy was a more burly character; here he's a slight young teen, but still with a remarkably useless power: he can remove his arm at will, while still controlling it. Just the one arm, though. Even though considered odd by most, he still dreams of joining the Legion and meeting Phantom Girl, "probably the least judgmental girl in the universe."

Meanwhile, PG, Cosmic Boy, and Brainiac 5 are helping a farming planet with a disgusting, tentacled monster; and Cos uses his magnetic powers to get PG to punch it in the see-through stomach. Still, her flight ring is bent, and as Arm-Fall-Off Boy makes his case, Starfinger attacks the Legion! Starfinger is played for jokes as well, although he does blow up a Legion Cruiser. I can't recall if either appeared on the cartoon series this book was based on, but they're pretty deep cuts for an all-ages title.