Ninja Cookie is an S-grade Cookie. He can jump more than the regular double jump. With upgrades, the player gets multiple jumps. The Cookie has the advantage of staying longer in the air meaning less chances of falling into holes due to missed timing.
No cookie knows the importance of training better than Ninja Cookie. But is it just training? The secret to his multi-step jump is unknown. Some say he steps on wind, others claim he is more than a Cookie. The higher his level, the more he can jump.
Ninja Cookie will knock over obstacles that are half-height (i.e. those that can be jumped over with a normal single jump) on his way down, but it will get hit from bigger obstacles and hanging ones. As the game is centered around regular and double jumps, his ability is considered little more than a gimmick that has no usefulness to normal runs in the game, although it may help for achievements based on jumping.
Unlike other S-cookies, Ninja Cookie only costs 89,000 coins, thus making it easier to upgrade to maximum level. Also, when you are about to run out of Energy, you can easily keep jumping in the air as Cookies cannot 'die' mid-air.
His ability is significantly inferior to that of other S-rank Cookies, as it only allows him to jump more than twice, which does not affect gameplay in any way other than increasing/decreasing the chance of crashing into obstacles or falling into holes.
Prior to Rebel Cookie's release in Kakao, a red version of Ninja Cookie was shown in a preview image. Inside the files was a functioning green placeholder version of Ninja Cookie that worked as Rebel Cookie does, bafflingly.