Wally West has proven himself to be a true hero as the Flash, saving the world just as many times as his mentor Barry Allen (if not more so); but the first superhero act Wally ever did was downright criminal.
Wally took on the mantle of Flash following Barry's death in Crisis on Infinite Earths. Since then, he's used his incredible speed to stop an absurd number of crimes and helped the Justice League save the universe just as many times. But before he graduated to be the Flash, he was a fan of the hero and nephew to Barry's girlfriend Iris West. Wally even served as Barry's sidekick before getting his powers, and truly stepped into that role after he gained his powers and became Kid Flash. But that almost didn't happen since his first ever act as a superhero was committing a criminal act, something his mentor Barry Allen didn't much approve of. But considering that Wally was literally 10 years old at the time, Barry decided to give Wally a warning. This was a smart move, considering Wally West saved the DC Universe.
Wally West Used His Power For Harmless Crime
Readers got to see Wally's irresponsible first use of his power in Mark Waid and Greg La Rocque's 1992 storyline "The Flash: Born to Run" from The Flash #62-65. After Wally West gains superspeed due to a freak accident, Barry takes him under his wing and begins training him on how to use his powers. But the first thing Wally actually uses his powers for, is running through town, looking at everyone and everything as well as stealing a police officer's hat right off his head. This is something Barry isn't exactly happy about, but Wally is eventually able to use this very crime to prove why he would eventually grow up to be the best true Flash.
Wally's Prank Comes In Handy
While Barry scolds Wally for his little prank, this prank actually ends up saving Wally's life and stopping a crime. When Mirror Master uses evil reflections of people to rob banks and commit other crimes, Barry is left stumped. It's only when Wally witnesses one of the evil reflections fleeing the scene of a crime that Wally decides to give chase to find where the Mirror Master has been hiding. Given the fact that he's 10 years old and this is the first supervillain he's faced, Wally knows he shouldn't take the Mirror Master on directly. However, he has no time to contact Barry and follow the reflection, which is why he decides to steal every hat he sees between him and Mirror Master's base. This harmless crime lets Barry track down Wally and save him from Mirror Master, it also demonstrates the difference between Wally and Barry in how they approach crimes.
While Wally West's prank is ultimately harmless and even comes in handy further down the road when he uses it to catch Mirror Master, it's still an interesting fact that when Wally West gains superpowers, his first act as Flash's sidekick is to commit a crime, even if it's a harmless one.