When he returns to Earth, Cliff crashes through a billboard advertising an autobiography written by the dinosaur half of Animal-Vegetable-Mineral Man, a recurring minor character from season 1. One of the people quoted on the billboard is Kite Man, a comic book villain who also appears regularly on the DC Universe's show Harley Quinn. His book blurb of "Hell Yeah!" is his catchphrase.
When Cyborg and company asks The Beard Hunter where Mr. Nobody is he tells them that "He got a gig on some animated bullcrap and haven't heard from him since" as he says this an ad for the DC Universe's show Harley Quinn appears in the corner on which Alan Tudyk voices the Joker and Clayface as well as Mr Nobody on Doom Patrol.
Kipling says Eismann threatened to feed him to a zombified alicorn. Alicorns are unicorns with Pegasus type wings; the image of winged unicorns dates back to ancient times. Recently, alicorns were popularized by the children's program "My Little Pony". Consider the twisted notion of any saccharinely twee cartoon character turned into a flesh eating zombie.