Reebok is catching some flak over the release of its Alien Stomper sneakers for Alien Day.

The shoes drew criticism from a number of Twitter users who weren't happy to learn that they were apparently produced only in men's sizes, despite being worn by a woman (Sigourney Weaver as Ellen Ripley) in the original Aliens.

CNET spotted a handful of tweets questioning Reebok's decision on sizing.

But, the brand says it did indeed produce the sneakers in small sizes that would allow women to pick up pairs and wear them comfortably. In a statement issued to CNET, Reebok claimed that the shoes were listed in men's sizes due to an error. The statement reads: "The Alien Stomper was mis-categorized on our US website as a men's shoe due a technical error. While size availability varied by market, the Alien Stomper is a unisex style and was produced in sizes (US Men's) 3.5 - 12, which is a typical size range for a unisex model."

Anyone still looking for a pair of Reebok's Alien sneakers is going to need to hit eBay and be ready to spend some serious cash.