Fans spot really strange cake detail in Olivia Rodrigo's birthday pics

Olivia Rodrigo turns 21 today, 20 February, and she celebrated her birthday eve with a tongue-in-cheek Instagram post that has had fans talking for several reasons.

First, the "vampire" singer made a cheeky joke in the caption, writing, "today is my last day of being able to underage drink (hypothetically) !!!!"

This, of course, is a reference to the drinking age in the U.S. being 21. She probably didn't want to outright admit that she has had alcohol before, but she's also very much making it sound like she has.

However, it was something else about the post that really stopped fans in their tracks: the picture of Olivia's birthday cake and the strange way it was sliced.

"What an unhinged way to cut a cake," one fan quipped.

Responding to the first fan, several others pointed out that *technically* the way Olivia and her friends had cut her cake is the most efficient way to do it.

"that’s actually the proper way to cut cake, at least wedding cake! my family owns a wedding business and this is how we have always cut cake. you get the most slices out of it," one person said.

Someone else noted: "i’ve seen some people cut it like that as a tradition and the middle piece is supposed to be the piece for the bday person"

Anyway, she may only be 21, but Olivia is absolutely thriving these days.

After getting her big break in Disney Channel's High School Musical: The Musical: The Series, she stole hearts everywhere with her devastating breakup song "driver's license," followed by the more upbeat breakup anthem "good 4 u."

This year, she's bringing the angst on her second solo world tour with two dates in London this coming May, when she will take over the O2. Good 4 her!