Cheddar is Dr. Brander's pet rat that she used as the subject for her prototype experiment of "The Noserator". Which she was using to cure those who suffer from nasal problems. Cheddar was shown to have almost no sense of smell, because of his running nose and constant sneezing. Once she used the device, he was cured but however this was only temporary. Cheddar was soon back to normal and revealed Chuckie would be too, much to Chas 's heartbreak. Dr. Brander decides to give Cheddar to Chuckie, as a sort of gift and as Chuckie said they belong together because their noses weren't work right.
You can find Cheddar gallery here.