The Yoshi Team is a group of variously-colored Yoshis that appears in some way in all three Super Smash Bros. games. (The name "Yoshi Team" is only used in the first game, but it can be assumed the later Yoshi groups are at least a reference.) Generally, the Yoshi Team appears in groups of two or three, with each member having below-average intelligence and being easy to KO.
In Super Smash Bros., the Yoshi Team is made up of 18 multi-colored Yoshis. They are the second opponent(s) the player faces in the 1P Game after Link. The Yoshis rarely attack, are very weak, and will be KO'd from almost any attack. They tend to jump in random directions, often off the edge. Killing them in the order they appear yields the Yoshi Rainbow bonus.
In Super Smash Bros. Melee, the Yoshi Team re-appears in the Adventure Mode, about halfway through the Mushroom Kingdom stage. There are only ten Yoshis in the team this time but act mostly the same. However, a complement of 30 Yoshis appear in The Yoshi Herd, SSBM's 24th Event Match, with the final one being a giant. Also, in the opening FMV, Yoshi is seen leading hundreds of other Yoshis at one point.
In Super Smash Bros. Brawl, the fifth Co-Op Event Match is The Yoshi Team of 50. The largest Yoshi Team thus far is even easier to KO than its predecessors, but on higher difficulties, the significantly reduced time alloted - combined with Brawl's relatively slow loading times - can make them quite challenging. There is also a mini-team of 6 Yoshis in Event 11: Yoshi's Rainbow, which must be KO'd in a colored order similar to the Yoshi Rainbow bonus.