The three monkeys go to see the big auto race, where Moe becomes to co-driver of Barney Hippo's car. While Barney is off getting lunch, a girl monkey comes by, climbs in, plays with the controls, and Moe and she are off on a random path.
It's a decent example of the short-lived series at Walter Lantz's studio, but clearly the need to introduce new characters meant that three monkeys were not enough to sustai the series. That happens eventually to all of them, but this is remarkably early in the game.