Always wondered who came up with that tagline. Art really does live on, and this is one of the best posters ever. You have to wonder, did they actually get a sketch or something of the egg, but see it upside down? The shape of the crack if you flip it does resemble one half of the cross-like flaps on the actual alien egg.
Something similar happened with the starship Reliant seen in Star Trek 2, where the producer saw the design upside down and said "brilliant!".