Mars Attacks' aliens only speak in variations of "ack, ack," which is actually a sly meta gag. Prior to directing Mars Attacks, Burton was coming off the back of some of his most acclaimed work. He balanced the hugely successful Invasion Of The Body Snatchers.
Unlike 1996's other alien invasion movie "Green, Green Grass Of Home" singer Tom Jones (as himself) and many more, though few of them make it to the end credits.
While Burton planned for Mars Attacks to use stop-motion effects, it instead used early CGI to bring the aliens to life. While these effects have undeniably dated, it helps that Mars Attacks' villains are already so cartoonish, resembling human skulls with oversized brains. Mars Attacks' aliens only verbally communicate with "ack, ack" noises, which was actually a placeholder written into the script. Mars Attacks' "ack, acks" were meant to convey when the aliens were speaking, with the production planning to develop a language and subtitle the vicious extraterrestrials later.
Mars Attacks Alien Dialogue Is An In-Joke
The screenwriters behind Burton's underrated Ed Wood Scott Alexander and Larry Karaszewski were brought on to Mars Attacks and did uncredited work on Jonathan Gems' screenplay. They recalled in a DP/30 chat about writing Mars Attacks' memorable "ack, ack" dialogue into their drafts just to denote when the aliens were talking. They were surprised to see that not only were they used in the final movie, but even the number of "acks" they wrote for individual aliens were kept, making for an odd meta gag.
However, there is a conflicting of how Mars Attacks' "ack, ack" speech came to be. According to an interview with Burton during the film's release, when the project was being storyboarded, somebody started saying "ack" into a tape recorder, and the idea stuck. In the fun Mars Attacks itself, a translation machine sometimes spells out what the creatures are saying, though "ack, ack" is the main way they communicate. Burton apparently resisted studio notes to subtitle Mars Attacks alien dialogue, likely finding it much funnier to just leave it to viewers' imaginations.
