Apparently, yes
Newer machines can be configured to examine a flash drive for an os. The Dell in front of me will. There's a version of Puppy Linux that's designed for launching from a flash drive (by virtue of being particularly compact). A fellow I used to work with wanted to be able to use Linux on his work laptop but didn't think the tech boys would be happy if he installed it as dual boot, so he'd use this particular version of Puppy.