Down tilt - A crouching kick that semi-spikes opponents.
Up aerial - Does an aerial flip kick. The last part of the attack semi-spikes. It is much more effective than in later games, providing high knockback and hitstun, and being a fairly easy way to intercept certain recoveries such as Pikachu's Quick Attack and Fox's Fire Fox, especially if they're recovering high.
Down smash - Does a split kick. It is very fast with good power and decent reach. It can be very effective if landed near the edge. It has noticeable ending lag however, and its edgeguarding capabilities are rather limited. More effective than in later games. In the Japanese version, it has a slightly less favourable angle.
Down smash - Does a spinning split kick. Low start-up lag and good power for a semi-spike. It has noticeable ending lag though, and with its very short reach, Jigglypuff is better off using its aerials for edgeguarding.