When the younger Danny and Karl are playing Striking Vipers, one of the game characters briefly shown on screen is a polar bear. This is an ongoing reference to white bears since White Bear (2013).
Pom Klementieff and Anthony Mackie appeared together in Avengers: Infinity War (2018) and Avengers: Endgame (2019) as Mantis and Falcon, respectively.
Ludi Lin plays Lance in Striking Vipers, a game that is very similar to Mortal Kombat (1992). Ludi Lin was in Mortal Kombat (2021) as the character Liu Kang.
The actors playing Danny, Karl, and the characters they each play in the game have all appeared in DC or Marvel films. Anthony Mackie (Danny) and Pom Klementieff (Roxette, AKA Karl's avatar) both appeared Marvel films as Sam Wilson/Falcon and Mantis respectively. Yahya Abdul-Mateen II (Karl) and Ludi Lin (Lance, AKA Danny's avatar) both appeared in DC's Aquaman (2018) as Manta and Captain Murk respectively.