Kerojii

The Four Wise Men (カエル四賢者) are four tiny, old, frog-like members of the Red Arrows Pirates who appeared in the sixth One Piece movie.

Appearance
The Four Wise Men are all, tiny and elderly and frog-like in appearance, hence their group's name. Despite their group's name, one of them is female. The group is composed of:

Personalities
Three of them anger Nami just after being introduced: Keroji believes that they are much wiser then the Straw Hats because of their age. Keroshot calls her immature for getting angry. And Keroko insults her by saying she's only a little younger then herself. The only member that did not take a hostile note to the Straw Hats upon introduction was Kerodeek, who just asked if he could take a nap.

Speedboats
The Four Wise Men used speedboats in the second Test of Hell against the Straw Hat Pirates. Despite the Straw Hats only getting simple speedboats, their boats were outfitted with various weapons and modifications that made them difficult to deal with, but they were ultimately destroyed by Zoro and Sanji.

Baron Omatsuri and the Secret Island
The Four Wise Men participated in the second Trial of Hell issued by the Omatsuri against the Straw Hat Pirates. The purpose of this trial was a race to the finish in which the first group to arrive at the finish line, wins.

However, it is evident rather quickly that the odds are against the Straw Hats: not only are their crafts outmatched but the Four Wise Men are experts at turning people against each other. This combined with the individual histories caused some members of the Straw Hats to fight among themselves, opening old wounds. While the opposition is eventually defeated, the unity of the Straw Hat crew is weakened, just as planned. Despite this their speedboats were ultimately destroyed by a combined efforts of Zoro and Sanji.

All four eventually died when Omatsuri was defeated.