Ninjis are a type of enemy that first appear in Super Mario Bros. 2. In Super Mario Bros. 2, they jump up and down continuously in place, and like most enemies from Super Mario Bros. 2, they could be picked up. They later appeared in Super Mario World and instead of staying in place and jumping, they would move around at a speed that's faster then Koopa Troopas, and when coming across and obstacle that's in the way, a hole in the floor, or a cliff edge; they'd automatically jump to get past it.
Ninjis reappear in Paper Mario: Sticker Star returning as enemies. They are fought most of every levels in World 3. They attack mainly by jumping at Mario and turning themselves into Throwing Stars and hurling themselves at Mario. They also have a habit of using decoys making to believe that Mario is attacking the real them. They have an HP of nine.
Their next appearance is in Super Mario Run. They have they same characteristics, but Mario can double jump off of them.