The popularity of TikTok is really based off of the ability to copy others. It's just a constant stream of "I can do this trend better than you can." That's what makes the app so successful. Not everyone can have a funny tweet, but everyone can do a challenge like the "is ur ass flat" check.
It goes like this: you put your connected hands behind both of your feet and then raise them up.
If you can get your connected hands all the way past your butt, unfortunately your butt is FLAT in the TikTok world. If you can't? You're a winner!
The physics behind this don't really make sense, but I don't think TikTok is the land of science. If you had long arms, you'd be able to accomplish this while still having a FAT ASS. All that being said, McKayla Maroney decided to get involved with this challenge:
She, in a surprise to nobody with a brain, passed. Nice to see some order in this world being restored.
If you haven't been keeping up with McKayla, she is a singer now:
I get some serious Ariana Grande vibes from listening to that. Not bad.