In the episode "Society of the Blind Eye", Stan lost his pen, mug, and notepad into a portal that went to another dimension. This was a reference to the episode Close Rick-Counters of the Rick Kind when Rick opened a portal, in which a pen, mug, and notepad came out. The Gravity Falls episode came out after the Rick and Morty episode.
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The SimpsonsIn the couch gag for the episode "Mathlete's Feat", Rick and Morty were seen crashing through the wall of the house, killing The Simpson family. Morty was terrified to see what he had done and Rick blamed it on him. He told him to go to another dimension with their family portrait and clone them to bring them back. Morty went there and while he did, Rick walked around the house, eating their food and drinking Homer's beer. Ned Flanders walked in and saw what he did and so Rick had to use his Freeze ray to freeze him. When Morty came back, they brought The Simpsons back to life, but they came out looking like mutated versions of themselves that resembled Rick because of their skin color and spiky hair. Knowing that there wasn't really anything else they could do, Rick and Morty quickly fled the scene, leaving them behind. After this, Bart decided that he had had enough and said "No more guest animators!"
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At the end of episode Analysis of Cork-Based Networking, Abed and Rachel are seen watching an episode of Rick and Morty. It should be noted that Community was created by Dan Harmon and main characters of the series make cameo appearance in Auto Erotic Assimilation.