Dug is a playful, optimistic, friendly, and lovable dog who is always kind to those he loves. He likes almost everybody he comes across. He is also very good at following rules and can be somewhat of an airhead at times. Dug also gets easily distracted by some things, mainly squirrels. He is a very social dog.
He is a fun-loving, dog who speaks English via a special collar that translates his thoughts into speech, invented by his former master, Charles Muntz. Early in the film, Dug, one of Alpha's canine minions, is searching for a large bird that Muntz has been trying to capture for decades. He runs into Carl Fredricksen, Russell, and Kevin (the bird he is searching for). However, immediately after meeting Carl, Dug begins to idolize him and sees him as his master. He winds up switching sides, assisting Carl, Russell, and Kevin.
He is every ounce a puppy in behavior and quickly becomes attached to Carl, who is at first hesitant to accept Dug. When he does, Dug expresses his joy in a manner that leaves no doubt that he prefers his new master.
During the end credits of the film, it's revealed that Dug had mated with another Golden Retriever (with similarities to him), and they had many puppies (probably much to Carl's grief); at least twenty of them that were caught on photo.
Dug appears in his very own short as the main character, as well as being the narrator.
The short takes place before Dug comes across Carl Fredrickson and Russell and also on Dug's birthday. Alpha, Beta and Gamma can be seen in the beginning chasing after Kevin only to have Dug let her get away. They then proceed to continue in the search for Kevin while trying to keep Dug distracted by doing various tasks such as, watching a rock and sitting still in a certain spot, but they end up backfiring on Alpha, Beta, and Gamma. However, towards the end, Dug decides to run away and ends up finding Russell and Carl, where it continues inside the rest of the film Up.Disney's Animal Kingdom. and Disney California Adventure as a meetable character.
At Disney California Adventure, Dug, along with Russel, appears at the Redwood Creek Challenge Trail in a Wilderness Explorer's Camp theme added to the attraction in June 2011. Guests can participate in various activities at the camp to earn badges and become Senior Wilderness Explorers at a ceremony held at the Ahwahnee Camp Circle.
- In the Monsters, Inc. comic book mini-series, Laugh Factory, when Sid breaks into Boo's room, Dug can be seen as a plush next to the Pixar ball.
- In Ratatouille, as Remy runs through an apartment building, Dug's shadow can be seen on a wall. Ratatouille was released two years before Up, but Up was in production.
- Dug has the same yelp as Scud.
- Dug was awarded the Palm Dog Award by the British film critics as the best canine performance at Cannes Film Festival, beating out the fox from Antichrist and the black poodle from Inglourious B******s.
- Dug is the only dog owned by Charles Muntz that is not named after a Greek letter. Interestingly enough, there isn't a dog named Delta seen in the film, so it's possible that Dug is Delta.
- Dug has a heroic theme that plays few times in the film, with the final time playing in a brief and deep emphasis when he is the new Alpha.