In the Flash comics, Edwin Gauss is an American physicist that becomes the Folded Man, a super-villain who uses a suit he built to travel between dimensions, able to become two-dimensional as well as four-dimensional. In the show, he is instead a hippie and his powers are in his genetics, and he is not evil. His powers have also changed from literally folding himself through two-dimensions and four-dimensions to entering pocket dimensions.
DeVoe uses Dwarfstar and Black Bison's powers to enlarge and animate a miniaturized T-rex skeleton and sends it after Ralph, saying "An old friend requests a rematch," referring to the events of "When Harry Met Harry" (2017).
When Harry throws around items looking for his Thinking Cap, Cisco calls him "Captain Caveman", referencing the title character from the TV series Captain Caveman and the Teen Angels.
When Edwin Gauss is describing The Thinker's lair and both Devoes,he refers to Devoe as looking like Professor X. Which is a reference to the Marvel character Charles Xavier A.K.A Professor X.
When Caitlin mentions leasing her "inner penguin spirit animal" she's likely making a fight club reference when Edward Norton's character "narrator" had the same spirit animal.