The Merch: Shortly after the release of "A Close Shave", companies took note of how merchandisable the characters were, particularly Gromit and Shaun. Plush toys, backpacks, key chains, alarm clocks and figurines are just a small helping of products you can find with their likeness slapped on.
The Other Darrin: Ben Whitehead has been increasingly acting as the voice of Wallace, most notably in the Grand Adventures series, along with a number of TV adverts featuring the duo. Fortunately Whitehead's voicing is so near to Peter Sallis that most people don't even notice the difference. The only exception was in "Fright Of The Bumblebee", the first game in the Grand Adventures series. As it was Whitehead's first time voicing Wallace, he sounds a little different than he usually does. Fortunately, he seems to have gotten much better as he continues to voice Wallace.
The Red Stapler: The last of the creameries manufacturing the centuries-old Wensleydale cheese were teetering on the edge of closure in the early '90s, until they received a chance mention in A Grand Day Out. Noticing the increased interest, the creamery persuaded Aardman Animation to endorse a Wallace and Gromit-branded cheese, which worked to rebuild Wensleydale into a thriving product worldwide.
Wallace was originally a postman named Jerry, but Nick Park felt the name did not match well with Gromit.
Gromit was going to originally be a cat, but then changed to a talking dog. Park originally wanted to voice Gromit himself, but his voice was recorded by Peter Hawkins. The idea of Gromit speaking was scrapped when it became clear how expressive he could be just through small movements of the eyes, ears and brow, so no voices for Gromit were ever used.
Write Who You Know: Nick Park has stated that Wallace is loosely based on his father, who also liked to tinker, with a little of his brother, an electrician, thrown in for good measure.