Heat Signature is a series of pre-war movies, which consists of at least three films. The film's tagline: "UNDER THE OCEAN NO ONE CAN HEAR YOU DIE" seems to suggest that it is a horror film or a thriller/suspense, though the actual genre is unknown. The film appears to be a fusion of horror and suspense, with the first film about a submarine crew who enter an area where they detect the enemies heat signature, but they are unable to find their own. In the episode "Heat Signature," a scene of the film is shown, and then the camera then moves away from Marceline's TV (the TV on which the movie is playing) and to Finn and Jake. The movie's audio is lowered so viewers can hear Finn and Jake's dialogue, but in the background noise what seems to be people screaming and some kind of monster making noises (roaring, snarling, growling, slashing, chewing, etc.) can be heard.
Heat Signature has been referenced in two episodes, "Video Makers" and "Heat Signature." In "Video Makers," the third film was set to appear as the movie during Finn and Jake Movie Club, but was canceled due to copyright warnings. In the same episode, Marceline seems to have prior knowledge of the movie, asking "Oh, with the submarine?" In "Heat Signature," which chronologically occurs before "Video Makers," Finn mentions how strange it is that Marceline is 1000 years old and has never seen it, both this and Marceline's previous comments seem to show that this movie was popular in its day. Finn also seems to like the movie quite a bit, stating that "it would blow their minds" in reference to Marceline and her friends who had not yet seen it.
The tagline of the movie make a reference to the tagline from the movie Alien from 1979: "In space, no one can hear you scream."
In Video Makers, at the beginning of the movie "Heat Signature 3," the words "Document 413" appear on the screen, suggesting that the warning Finn and Jake read is not the normal warning that appears before a movie starts, but a message stating that it was classified information, and that Heat Signature (or at least what Finn and Jake have mistaken for "Heat Signature 3") is not a movie at all, but government security footage of real events that happened before or during the Mushroom War. Additionally, the number 413 is associated with the webcomic Homestuck, and is a plot-significant number in the comic. Several staff members for Adventure Time have verified that they do enjoy the comic, and there are other references to it in other episodes.