It is possible with the right kind of arduino chip and the right firmware for it to make something that looks like a USB drive. (At least I think I figured out that was possible once).
I keep hoping someone will combine that with a network interface so I can make a NFS or CIFS filesystem appear to be a thumb drive to a stoopid TV that refuses to read file shares, but can play anything from a thumb drive.
So far, I haven't seen such a gadget. (I wonder what the response would be on kickstarter, but I'm not gonna implement it :-).