The Duck Brothers are a trio of alien siblings, primarily featured in their eponymous episode.
They are a very argumentative group, clashing on a multitude of arbitrary reasons, especially their tendency to lay eggs. Rather ignorant to common sense, the brothers seem to take a more complicated, assumptive route to accomplish simple tasks, a choice that they will later blame on each other. Despite this, they share a brotherly love, and are there for each other when needed. At least two of them can play guitar.
When their brother was taken by a chef, the Purple and Green ducks planned a scheme to rescue him by mind-controlling a nearby owner. They had almost completed their goal when the woman's dog intruded and stole their remote control. Unwilling to let their brother be cooked, they captured her husband, and returned to face the dog. A battle ensued between the possessed humans, with the Duck Brothers on the losing end. Depressed over the assured loss of their sibling, Courage offered to help them out. He broke into the building and completed Muriel's task, and the brothers were reunited (Ep.6-1).
Two of the brothers made a cameo in the episode Ball of Revenge: being musicians for the half-time show. It's never stated why or if the brothers are still antagonistic to Courage, but they never interact with Courage or the other villains beyond this musical number.
- Contrary to popular belief, the Duck Brothers are not voiced by Ringo Starr of The Beatles, as confirmed by John R. Dilworth himself in an interview with RebelTaxi of Youtube. 
- The Duck Brothers' real names are unclear.
- For some reason, the green-eyed duck brother doesn't return in Ball of Revenge.