The Three Blind Mice are identical white mice brothers that are blind and can't see anything throughout the entire course of the films. They are based on the nursery rhyme characters of the same name.
The mice were banished into Shrek's swamp by Lord Farquaad. Shrek notices the Three Blind Mice first, walking over the table. They show up at Shrek and Fiona's wedding where they are turned into two horses and a carriage rider by a fairy Godmother.
In this film, the mice have a larger role. They are three of Shrek's friends who watch his swamp while Shrek and Princess Fiona are visiting Far Far Away. Later, along with Gingy, Pinocchio, Big Bad Wolf and The Three Little Pigs, they save Shrek from the Fairy Godmother and join the dance during the end song "Livin la Vida Loca."
The Three Blind Mice join Shrek and the others for Christmas at Shrek's swamp.
They made cameos in the normal universe, celebrating the Ogre Triplets' 1st birthday.
They were seen in Shrek's swamp with Donkey, Puss, Three Pigs, Gingy, Pinocchio, and Wolf at the beginning. Later on, it's revealed that they never made it to Duloc to tell scary stories, as they were walking in circles on a mini turning table.
The trio were mentioned in the episode "Shrek Reacts to 3 Blind Mice", where they were heavily criticized for their play The Butcher, the Baker, and the Candlestick Maker.