Shamus is shown to be kind toward John, Annabel, Georgie, Mary Poppins and Jack. He even praised them for helping fix his carriage wheel. Just like his horse, Clyde, he is able to talk. He speaks with an Irish accent.
Shamus is described as a dog who is part poodle when he introduces himself and like all the animals in the animated sequence, he is anthropomorphic.
Role in the film
When a fight over the bowl accidentally causes it to crack, Shamus and Clyde tell John, Annabel, and Georgie that that caused their carriage wheel to break. Mary takes them and Jack inside the bowl to help fix the wheel. When John, Annabel, and Georgie ask for a ride because they feel the trip is too short, Shamus and Clyde give them one to the music hall.
Later, when Georgie gets kidnapped by the Wolf and his accomplices, the Badger and Weasel, Shamus and Clyde help John and Annabel get onto the wagon carrying him. Fortunately, they manage to do so.
- Chris O'Dowd also portrayed Richard in the Marvel Studios film, Thor: The Dark World.
- He was originally going to voice Tigger in the Disney live-action film, Christopher Robin as this would have been his first Disney role in 2018 while Shamus would be his second role in the aforementioned year. However, his test voice for Tigger was negatively received by fans for his participation as Tigger; as a result, Jim Cummings replaced him in the final version of the film, who also voiced Pooh in it.
- In an early version of the film, Shamus was originally an anthropomorphic horse, not a dog and his transportation included two human guards instead of a talking horse prior to the animated sequence being changed into the final version. Additionally, one of his lines "Well, of course she can talk" was given to his steed Clyde in the final version of the film.
- Deleted song - The Anthropomorphic Zoo (Mary Poppins Returns; Blu-ray).