Nagrarock turns enemies into frogs. You can get them by poaching Porkys, so not a big deal if you don't get one here.

The ninja sword is Sasuke Knife: one of the three unique ninja swords and the third most powerful in the game. Worth getting if you want everything.

BTW, I tried Chicken once and my character ran and hid in a corner for four turns. Not really recommended. Threaten is better IMHO.