Board Thread:Off Topic/@comment-28716546-20160825172539/@comment-24922135-20160826165759

Examples of aliens/species from media you could use as a shapeshifting alien include the T-1000 from Terminator, Prisoner Zero from Doctor Who, Oolong from Dragonball, and Changelings from My Little Pony. It is surprisingly hard to think of shape shifters from media that I could list here.

I have now remembered that there are also human-like changelings from Monster Musume (nudity warning if you want to google that manga/anime). Slimes in that universe also possess a high level of shapeshifting.