The Question: Is it David who contaminates Prometheus?
The Viral: In his "Happy Birthday" video, attention is drawn to David's sense of curiosity. He stares at a flower with a sense of rapture, and explains that he thinks about "anything". Indeed, Fassbender describes him as almost childlike in his outlook on the world.
Could it be this curiosity that is the crew's undoing? In the trailer we see David examining one of the nascent life-forms with a strange expression on his face, and then later, we see him removing what looks like an egg from one of the pods found in the temple. Should he really have brought one of those back to the ship?
Our Best Guess: We reckon this is how that weird facehugger-ish creature makes its way on board, assuming it's the same thing we see terrorising Charlize Theron later in the film.