Funny and probably not serious. Propagate is a pretty dangerous mechanic, maybe include "nontoken" into it to keep your tokens from getting out of control, even if it makes this card not work as well anymore.

Mmm... the mechanic is Clone, with a drawbacks of nly working on your creatures, tapping then, and having to have a second creature sharing a type too.

Certainly not something you can have much of in a set, though.

Oddly I also think nontoken - because otherwise it'll get very samey. You'll keep cloning the same creature, and keeping a copy of it alive over and over. Not so much to prevent "An army of tokens" arriving; as this mechanic only creates one it's not so bad for that.

I just find it interesting comparing this to Battle Screech.