Radial Hypoplasia is a mutation that can be found in some cats--called Squittens (for Squirrel Kittens) or Kangaroo Cats--and is recognized when the front two legs are not developed fully, leaving them small and short and giving a sort of 'kangaroo' look to the cats.

I'm not a programmer or anything, and I'm unsure if this mutation should be lethal or not, so I'd like to hear your guys' ideas on this as well!

Edit: I'm going to leave this up for now, but yes, the idea has already been addressed in the mutations master post.