Beta and Gamma

Beta and Gamma are two dogs owned by Charles Muntz in Up. Beta is a Rottweiler and Gamma is a Bulldog. They are second- and third-in-command, and are usually seen with Alpha. Beta is voiced by Delroy Lindo and Gamma is voiced by Jerome Ranft.

Up
Beta and Gamma are Alpha's 2nd- and 3rd-in-command. Like Alpha, they both wear a translation collar that enables them to talk. They were sent on a mission to find a giant bird and bring it to their master. They later encounter Carl Fredricksen, Russell, Dug, and Kevin and take them to their master, who turns out to be an elderly Charles Muntz, Carl's childhood idol. After learning about Russell's friendship with Kevin (the bird), Muntz furiously sets Beta and Gamma, as well as the rest of the pack, on the four misfits.

Beta and Gamma are later seen driving biplanes. Outside, Russell sees Carl and Kevin in trouble. Encouraged, he manages to climb to the porch of the house. Planes continue to attack, but he manages to stop the planes by calling out that he sees a squirrel; this distracts Beta and Gamma, as well as the other dogs, and makes them collide all of the planes, though the dogs parachute to safety.

Beta and Gamma are seen again at the cockpit. As Alpha tries to avenge Dug for losing Kevin earlier, Dug cleverly sticks a lampshade over Alpha's head, breaking his collar, returning his high-pitched voice, and trapping his head in the steering wheel. Believing Alpha is now wearing the "Cone of Shame," Beta and Gamma, as well as the rest of the the pack, take Dug as their leader and listen to his every command. They even take on Dug's personality.

Beta and Gamma are last seen among the other dogs at Russell's ceremony. They howl with approval after Carl awards Russell the grape soda badge from his deceased wife Ellie. Presumably, Beta and Gamma become Carl's pets in the closing scenes.

Dug's Special Mission
Beta, Gamma and Alpha are tripped by Dug, causing them to lose Kevin. When Alpha gives Dug "special missions," Beta and Gamma show support, but they get hurt along the way and almost killed. They eventually leave Dug while Alpha calls "master" to tell him that Dug caused them to lose the bird, and that he is a bad dog.

Trivia

 * Beta and Gamma are two of the three types of radiation in real life, along with Alpha.