DAN HARMON HAS A CAMEO IN THE END TAG OF INTRODUCTION TO FINALITY!
“Channel 101 Dan Harmon(s) over there on the right. So is 2 girls 1 cup. That’s horrible” - Yvette Nicole Brown
Look at the thumbnail that says Necropolis Pizza in the top right. Totally fitting that Dan appears in the final scene at the end of season 3.
…I’m guessing they edited out the 2girls1cup thumbnail before this aired.