How To Spot The Difference Between Mary-Kate & Ashley Olsen On Full House

Before they became the most famous twins in the world, Mary-Kate and Ashley Olsen were just two baby girls playing the same character (and occasionally cousins) on "Full House." The twins started filming as Michelle at just 9 months old in 1987 and continued the role until the series ended in 1995. Throughout the famous sitcom, the twins continued to look exactly alike, making it nearly impossible to tell which Olsen was saying, "You got it, dude!" during any particular episode. But members of Mary-Kate and Ashley's Official Fan Club could always tell (is this something we can put on our resume?) based on a few clues.

One of the easiest ways to tell which Olsen twin is playing Michelle is if they are using their left or right hand. Ashley is right-handed, and Mary-Kate is left-handed, which is why Michelle Tanner is known as ambidextrous and can switch dominant hands when eating, playing ball, or writing. Mary-Kate is also one inch taller than her twin, but that's hard to tell when they aren't on camera at the same time.

Another way to tell whether Michelle is played by Mary-Kate or Ashley is by looking at what type of scene it is. Mary-Kate would often do the funnier scenes, while Ashley would handle more of the heart-to-heart moments that the show was famous for. This could be due to their differing personalities, which their "Full House" co-stars, Jodie Sweetin and Andrea Barber, revealed in a November 2025 episode of "How Rude, Tanneritos." "Mary Kate did not like being sort of out on set, but Ashley was like, 'Cool, whatever,'" Sweetin revealed. "She was much more kind of docile about it." 

Don't feel too bad if you still can't tell the difference between the Olsen twins during the "Full House" years — even they can't tell themselves apart! In an April 2014 appearance on "The Ellen DeGeneres Show," even the twins didn't know who was who in early episodes. When host Ellen DeGeneres asked if they knew when Michelle Tanner was played Mary-Kate or Ashley in the series, Ashley responded, "Sometimes," and Mary-Kate added, "I think when we got a little older..."

But when DeGeneres showed them adorable baby photos of Michelle from old "Full House" clips, they could only guess who's who (just like us!). There was only one exception: in one picture featuring both of them as babies sitting side-by-side, Ashley knew she was the one on the left with a curious, wide-eyed look. Her reasoning? "Mary-Kate still makes that face today," Ashley said, referring to the baby's scrunched nose and turned down mouth, which looks like she was deeply disapproving of something off-camera. Mary-Kate, despite having had a stunning transformation since she was a kid, did not disagree, making the audience laugh.

One thing's for sure: Mary-Kate and Ashley Olsen's looks have changed over the years. Now, it's easier than ever to figure out which one is which when they make rare public appearances as adults.