A large piece of tubing on the side of a telesthetic chair with an Abomination strapped in it is labelled with '1.21 gigawatts.' This is the amount of energy Doc Brown states is required to travel through time.
An achievement / trophy called "Stick Around" can be unlocked by pinning ten enemies to the wall. In 'Predator' Dutch (Arnold Schwarznegger) pins an enemy to a wall by throwing a combat knife, before uttering the same line.
The text "liberate tutame ex inferis" ("save yourself from Hell") comes from the movie Event Horizon (1997) and can be seen on a floor in F.E.A.R. 2, written in blood.