Super Mario RPG has a challenge to complete 100 consecutive jumps on a single enemy. The reward is a powerful piece of armor for Mario.
It is recommended to do this in Mushroom Way (the zone directly after Mario's Pad), where you can find Spikey enemies which take no damage from jumps, allowing you to try again and again without re-entering combat with other enemies. Plus, there is a mushroom in a chest in the area northwest of the spikeys so you can refill on flower power!
I couldn't get beyond 30 jumps doing it by hand, so I found another way.