It's not every day a celeb is asked to pick a favorite sib on live television. We imagine it's even trickier when the sisters in question are Mary-Kate and Ashley Olsen!

During her Feb. 19 appearance on 'Watch What Happens Live,' Elizabeth Olsen a caller forced her to choose between her two older sisters.

"You have two sisters, I also have two sisters. You have to prefer one over the other," the caller said as Elizabeth made a "yikes!" face. "Who do you like better: Mary-Kate or Ashley?"

"There has to be one that's more in your favor today, that you're more vibing on," host Andy Cohen agreed.

"Ashley remembered my birthday," Elizabeth began, adding, "But I don't hold grudges against Mary-Kate forgetting mine?"

The actress justified MK's slip-up by adding that her sister was out of town -- and she should have just chosen her brother!

In case you didn't follow Elizabeth's aversion of the question, Andy confirmed, "To clarify, you're feeling closer to Ashley today."

Elizabeth laughed, promising, "Mary-Kate is literally going to come home from her vacation and shoot me that I said that."