You Were Yourselves Yesterday...What Happened?!

"Something's very off today, but I can't put my finger on it! All I remember was trying to move that stupid mirror of Stan's into Soos' break room yesterday, and then I ended up crashing out in the evening! And now I wake up the next morning to THIS?! GAH, I'M FREAKING OUT!!!"

Something tells me that the mirror is culprit here, but what do I know...

Gravity Falls - (c) Alex Hirsch/Disney