Mary-Kate and Ashley Olsen are perhaps best known for their side-by-side starring roles in film and television, including their breakout role as Michelle Tanner on Full House and their cult 2004 comedy New York Minute.

One lesser-known on-screen gig, though, is the twins' short-lived animated series Mary-Kate and Ashley in Action!, which aired from 2001 to 2002. The cartoon ran for just one season on ABC during Disney's One Saturday Morning block before it was canceled due to low ratings.

Mary-Kate and Ashley in Action! was the last TV series to officially star Mary-Kate and Ashley together.

The cartoon featured the Olsen twins as special undercover agents, in the vein of other popular 2000s cartoons such as Totally Spies and Kim Possible.

The twins voice acted as their spy alter egos, with Mary-Kate as Special Agent Misty and Ashley as Special Agent Amber.

As spies, the girls fought campy villains such as Renee La Rouge, an evil cosmetics mogul who attempted to take over the world with mind-controlling makeup, or Clive Hedgemorton-Smythe, who tormented the twin spies with his collection of stinky cheeses.

During production, the show was originally planned as a 52-episode series — the cartoon standard at the time — but only 26 episodes ended up airing.

After the cartoon's cancellation, its episodes were used as fodder for a spin-off book series about the twins' spy adventures in places such as Paris, Rome and New York City.

Sadly, the series marks the last TV show the Olsen twins worked on together following their sitcom and third television series So Little Time, which aired on ABC Family in 2001 and early 2002.

However, the Mary-Kate and Ashley did go on to make a handful of direct-to-video movies, as well as their 2004 theatrical release New York Minute. They also appeared on The Simpsons and Saturday Night Live as themselves the very same year.

Since then, the Olsen twins have made scarce film appearances, with Mary-Kate's last project being Beastly in 2011 and Ashley staying away from acting completely.

These days, they're focused on their fashion empire, which includes their line Elizabeth and James. They also serve as members of the Council of Fashion Designers of America and are the creative directors of Superga shoes.

Teen TV Stars of the 2000s: Then & Now