Last week, Selena Gomez released her music video for "Bad Liar" and a perceptive fan noticed that her BFF Taylor Swift made a cameo in it... well, it looks like Selena has a habit of asking her friend to make cameo's, because she was also in the show 13RW.
It's a major "blink and you'll miss it" moment, but it's there.
Tumblr user notes that Tay makes a brief appearance in Episode 10 of the series.
Tyler is talking to Sheri in the hallway of Liberty High, and there is a poster in the background.
If you pay close attention, you'll see that it's Taylor's album, 1989.