For people who’ve made action-focused western animation a key part of their life, 2005 is an important year. It got off to a great start with *Avatar: The Last Airbender, *which helped get the non-converted into anime and serialized storytelling that felt mature to anyone in its intended target audience back in the day. At the end of that same year, the demographic got *Ben 10, *a show equally as important as *Avatar *but in its own way.

The debut project of animation studio Man of Action and first released December 27, 2005, the Cartoon Network series follows a 10-year-old kid named Ben Tennyson who finds an alien watch called the Omnitrix, which lets him morph into one of 10 aliens for 10 minutes at a time. With Ben, his cousin Gwen, and their Grandpa Max spending their summer vacation traveling the country, each episode had Ben use a handful of aliens to fight villains like monster clowns, secret orders, and other aliens looking to take the Omnitrix for themselves.

On its face, it’s a pretty simple idea for a kids’ show, but execution-wise, it was basically perfection. Man of Action’s founding team was comprised of American comic book writers and artists like Joe Casey and Duncan Rouleau, whose collective credits included Marvel, DC, and Image Comics. Once you know that pedigree, it’s just a matter of clocking what influences run through the show, like the Kirby Krackle or Kevin Levin being a mashup of Super-Skrull and Metamorpho. What made it work was the earnest playfulness that ran throughout, whether it was that still-catchy theme song or Ben’s aliens themselves. The way he slams that dial and transforms, who wouldn’t want to be something called XLR8 or Four Arms?

So it’s not surprising that *Ben 10 *became a big deal for Cartoon Network with a four-season run, three movies (one of which was live-action), and a tie-in video game. It’s also not surprising that it went on to become a franchise that’s gone on to include more films and games, toys, and three sequel series in Alien Force, Ultimate Alien—which turned 15 earlier this year—and Omniverse. For Cartoon Network, this was its Avatar: something geared toward kids but that also had the good sense to age up with its audience. With Ben, Gwen, and Kevin made into teenagers, viewers had their own Spider-Man, even before Ben’s teenage actor Yuri Lowenthal wound up becoming Spider-Man.

In fact, they had something better here: *Ben *was an original property and therefore its own source material. So unlike the animated adventures of Spider-Man, Batman, or other big-name heroes going on at the time, you could watch any *Ben *show and be constantly surprised on a week-to-week basis without having a nagging thought in the back of your mind about things being undone or interfering with things going on in other parts of the same universe. There was a lot that went on from *Ben 10 Classic *up to *Omniverse, *with continuity mostly maintained, and all of it in conversation as the shows hit about every major superhero comic trope or storytelling device when all was said and done. (A lot of that can be attributed to comic book writer Dwayne McDuffie, who co-developed and did a lot on *Alien Force *and *Ultimate Alien *up until his passing in 2011.)

That *Ben 10 *was such an ongoing success had the added effect of bringing more action-oriented shows to Cartoon Network’s lineup, whose output at that point consisted of short-lived originals like *Megas XLR *or *Juniper Lee *and the occasional DC series. But because of *Ben, *we got *Generator Rex *and Secret Saturdays. The former was Man of Action’s second animated series, set in its own separate universe and based off an old Image comic made by Casey, Rouleau, and Aaron Sowd. While *Rex *and *Ben *crossed over in the Heroes United special, the former didn’t have quite the same staying power as its predecessor. The same could certainly be said for *Secret Saturdays, *which began the same year as *Alien Force *and whose cast eventually appeared in *Omniverse. *

© Cartoon Network

Neither *Rex *nor *Saturdays *was bad, and they might be worth a watch now, but their individual vibes didn’t entirely hit like what *Ben *had been providing for what was half a decade at that point. They also just didn’t arrive when *Ben *did. In 2005, superhero fever was taking over the world, and by 2008, the genre was actively making a go at becoming the dominant culture. Kids were eased into this thanks to *Ben; **Alien Force premiered days after the original show *ended, which was also weeks ahead of the first *Iron Man *and months before *The Dark Knight. *

It was (and maybe still is) an incredibly confident move on Cartoon Network’s part that led to a multimedia franchise that’s become part of its brand and allowed for *Ben 10 *to endure for so long. After a divisive reboot wrapped back in 2021 with its own respectable run—four seasons, a movie, two games, and specials that allowed for crossovers with both *Generator Rex *and its old self—Man of Action hasn’t entirely let go of its original creation. The studio’s apparently got comics in the works and will likely keep trying to get another live-action movie off the ground after the initial attempt failed, not to mention Rouleau has mentioned it could warrant an adult-oriented sequel in the vein of *Samurai Jack *or Fionna and Cake.

Such an idea feels antithetical to what made the original shows so successful, but what would *Ben 10 *be if it didn’t go out on a limb and see if that gambit worked?

Want more io9 news? Check out when to expect the latest Marvel, Star Wars, and Star Trek releases, what’s next for the DC Universe on film and TV, and everything you need to know about the future of Doctor Who.