Специально для ктулховUFO Defense was strongly based on UFO culture, but Terror from the Deep had a different source of "alien" infestation. It was strongly influenced by Cthulhu Mythos. Cthulhu is an unearthly amoral god created by H.P. Lovecraft, horror and science fiction writer. The main adversary of Terror from the Deep is clearly based on Cthulhu, as his origins and appearance are very similar, and the final assault takes place on the city of "T'leth" (analogy to R'lyeh, sunk underwater city where Cthulhu permanently sleeps). The final enemy is just a tomb with the face of "The Great Dreamer" (which is Cthulhu's octopus head), where he sleeps. The "aliens" are now hybrid creatures called The Deep Ones, which is a direct reference to Lovecraft's Deep Ones, ancient race of hybrid Cthulhu followers. (See more references the game had in Cthulhu Mythos in popular culture).
От так-то.
Да, и ещё... Комикс Hello Chtulhu