The dog of Old Lady Munson, who had him since he was a puppy, as seen in Search and De-Toy in Burt's flashback of when he was Coop age. Growler is a secondary character, although he is seen more than the other secondary characters. Growler may look scrawny and daft, but he is pretty tough. This is seen in the title sequence when he yowls (barking, howling and growling) at Coop & Kat. This is probably because he has always lived with the extremely nasty Old Lady Munson who probably taught him all he knows on misery, pain, wimps, boys and Captain Blasteroid, Old Lady Munson's nephew, as seen in Outer Space Case when Coop and Dennis become curious about Old Lady Munson's little guest. Growler is a good name for a dog that growls because his name starts with a growl and is a guard dog to Old Lady Munson. She barks a lot of time.
- Mrs. Munson dresses him in fleece.
- He is a good friend to Fiona.
- Growler barks a lot.
- In the episode "When Bad Dogs Go Big", Growler was as big as T-Rex.
- He seems to have more than 40 years of age, and the strange thing is that dogs live only the common mind to 15. He may not be the same dog because he seems too youthful for dogs that old.
- He has a resemblance to Oscar, a dog of our ally: Kick Buttowski.
- In one episode (when Burt was small) Growler was identical to Kick Buttowski Oscar.
- Growler hates cats (natural enemies) especially Kat.