Cult Film, TV, Geek Art
Tom Servo, Crow T. Robot and Gypsy from Mystery Science Theater 3000 made a cameo appearance in the background of Rick and Morty episode one.
If you look closely you can find more possible references like an Alien Xenomorph, the Mooninites from Aqua Teen Hunger Force, a prawn from District 9, Big Bird from Sesame Street, Space Invaders and more. Here’s a reddit post discussing it.
Rick and Morty creators Justin Roiland and Dan Harmon are also writing for the new MST3K reboot.