"I got a fake positive pregnancy test and fake ultrasound picture," she wrote at the beginning of the video. "Let's prank Erik that I'm pregnant."
When she shows him the test, Erik keeps asking her if it's a prank, saying "it will be really bad" if it isn't and when she swears up and down that it isn't, Erik gets REALLY upset. "You cheated on me," he accuses, to which she tells him "it's yours, you idiot."
Then, Erik drops a big bomb on her. "So you cheated on me," he repeats. "Don't you understand, I can't have children! So if you're pregnant, it's not mine, you cheated on me." Then, he breaks down into a totally convincing cry-fest.
But, the joke is on Erik's girlfriend, because just when she's starting to feel like the most horrible person EVER, he cracks up and tells her he was one step ahead of her. He knew about the prank and HE was pranking her.