Oppenheimer returns in Call of Duty: Black Ops 4 where he is mentioned in a cipher from the Zombies map Classified, where his chalkboard is a part of Ultimis Richtofen's demands.
Manhattan Project[]
Oppenheimer is known as the "father of the atomic bomb" for his role in the Manhattan Project. In Kino der Toten, one can find letters on the floor, saying "Manhattan Down". The testings of the Atomic bombs, known as Trinity, are the inspiration behind the Multiplayer map Nuketown and the Zombies map Nuketown Zombies. In fact, the word Trinity is the name of Nuketown's street, as seen in a sign in the map. In several Zombies maps, such as in The Giant, there is a chalk drawing saying "Embrace the trinity and true power will be yours".
Oppenheimer's famous phrase, quoted from the Bhagavad Gita: "Now I am become Death, the destroyer of worlds.", has been used several times, including in the Vbush files and a quote from the Zombies map TranZit.