According to the Los Angeles Times, Seth Green spent six weeks in a special sensor-equipped performance-capture suit while performing his lines as Milo. During post-production, the filmmakers noticed that Green was able to physically imitate the movements and behaviors of a 9-year-old boy, but his voice sounded too mature for the character. His voice was replaced by that of 11-year-old Seth Dusky. Green's voice still appears as the voice of one of the hippies on the '70s television show Ki watches. The first trailer, which was published on November 22, 2010, features Green's voice for Milo intact, implying that Dusky replaced the dialogue very shortly after this trailer was released.
This movie grossed $6.8 million in its opening weekend, which is the 49th-worst opening ever for a film playing in more than 3,000 theaters, and one of the worst openings for a major 3D release. With a budget of $150 million and a total gross of just $39 million, this movie is considered a massive box office bomb, and has the worst-ever financial reputation for a film branded by Disney. Its commercial failure contributed to Disney canceling its planned remake of Yellow Submarine (1968), which was to be made with the same motion capture technology.
The makers came up with their own alien language. Elisabeth Harnois stated in an interview that she and the cast were given scenarios by Simon Wells to which they acted out responses in improvised Martian language.
The movie is an adaptation of the book Mars Needs Moms by Berkeley Breathed, the creator of the comic strip Bloom County/Outland/Opus.
Simon Wells landed the directing gig because of his close association with producer Robert Zemeckis. The two had worked together on Who Framed Roger Rabbit (1988), Back to the Future Part II (1989), Back to the Future Part III (1990) and The Polar Express (2004).