Just watched Enemy Mine, and am pretty sure that it fits in with mpreg. What other movies are there that fit in with mpreg? Only others I can think of (that I have watched) are Junior (Arnold's character) and the Alien series (the chest births).
"Mainstream Mpreg" by Mprego2 (also here in the "Media Sightings" board, up in the "Important threads" section at the top) does list different media, including movies.
For me, movies like "Enemy Mine" are somewhat debatable in classifying it as "Mpreg", because even though the character in question was played by a male, the fictional species only had one gender (it's mentioned in one of the voiceover sections in the beginning of the movie that they are neither male nor female, but both) and reproduce asexually. (It's the same for some other areas as well, like the "Ben 10: Alien Force" episode listed in the "Mainstream Mpreg" thread - the conciousness might have been that of a human male, but the body was of a species that reproduced asexually, and may have also, going in a roundabout way, had only one gender.)