Beta and Gamma are Alpha's lieutenants. Beta is a Rottweiler and Gamma is a Bulldog. Like their boss, they both wear translation collars that enable them to talk. They were sent on a mission to find a giant bird and bring it to their master, although Dug was initially assigned this task because he was a disgrace to the pack and they wanted him gone.
Beta and Gamma later encounter Carl Fredricksen, Russell, and Dug. After some conflict, they take the trio of misfits to their master, who turns out to be an elderly Charles Muntz, Carl's childhood idol. Inside the dirigible, numerous photos, drawings and pieces of information on Kevin (the bird) can be seen. Carl soon realizes what is happening--Muntz is searching for Kevin. Carl hastily rushes Dug and Russell outside. Beta, Gamma, and the pack immediately give chase after understanding why they suddenly left, but fail to catch them.
After returning to the dirgible, Beta and Gamma explain to Muntz that Dug was with the the trio and helped them escape. Muntz tracks them on Dug's collar and captures Kevin. Beta and Gamma are briefly seen playing poker on a card table in Muntz's Spirit of Adventure airship.
Beta and Gamma are later seen piloting 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, Gamma, and another dog, causing them to collide all of their planes, though the dogs parachute to safety as Gamma declares his hatred of squirrels.
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 the pets of residents at the Shady Oaks Retirement Village after Dug became the new "Alpha" of the dog pack.
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 get hurt along the way and almost killed. They all eventually leave Dug, with Alpha calling him a bad dog.
- The dogs who are seen playing poker is a tribute to the famous Dogs Playing Poker series of paintings by Cassius Marcellus Coolidge.
- Beta and Gamma are Greek letters of the alphabet, along with Alpha.
- It is unknown how Beta and Gamma got back on the blimp when they parachuted to safety from their biplanes, although Carl, Russell, and Dug might have picked them up while they were returning Kevin to her babies.