XCOM: Enemy Unknown - Engineering Aliens

There's an article-style interview with Firaxis executive producer Garth DeAngelis ready for consumption over at IGN, with the topic of conversation being the "engineering" of aliens and the challenges involved with making them believable to us humans.
(Obviously we used the original UFO Defense as a lot of the primary inspiration,) said DeAngelis when pressed about the inspiration for the alien design, ([Lead Designer Jake Solomon] wanted to see the classic aliens come back in our re-imagination.) This presented a challenge to the art team, because the team wanted to stay true to the original, but also bring them up to speed, make them feel relevant to an audience in 2012, but without undoing the classic, "B-movie camp and UFO lore,) that informed their design.

To this end the team largely maintained the look and feel of the original aliens, right down to the original pitch ideas that featured the classic (grey) aliens called Sectoids. (I think that's important in our world: setting the framework for the player to reiterate, '˜This is an alien invasion.' Having something like the classic big-headed alien with big eyes that everyone knows and loves and then meandering from there into some more wild territory with things like the Floaters and Chryssalids.)