"Human Music" from #1.4, M. Night Shaym-Aliens! (2014), can be heard when Rick, Morty, and Jerry enter the Jerryboree.
The Jerryboree form reads as follows: Jerryboree Inc. (date) (Name) (planet), (dimension) (dimension of your Jerry) First drop-off? (yes/no) Desired length of stay: (unknown/forever) Does your Jerry have any allergies? (yes/no) Please indicate any existing physical damage (diagram of a body) Reason for drop-off: (Earth under siege/threatened to tell Beth/unwanted stowaway/annoying me)
When Rick and Morty arrive at Blips and Chitz, Mr. Meeseeks from #1.5, Meeseeks and Destroy (2014), can be seen talking with an alien whom is playing a game. When they cut back, he disappears after he "fulfills his purpose," which is likely due to helping the alien.
Fart's music/vocal style is a clear reference to David Bowie, who was well known for his out of this world and space-themed works, especially his song "Space Oddity".
There is a "Hungry for apples?" banner from Jerry's failed apple commercial in M. Night Shaym-Aliens! (2014) appearing in the background during the poker game at Jerryboree.