Russell is the tritagonist of Middlemost Post. She is a pet magic walrus whose stomach is so vast and huge that it doubles as a storage room for the Middlemost Post Office. She works with Parker and Angus to deliver mail across Mount Middlemost. She is the team pet for the Post Office.
Russell is a purple walrus with violet spots and fins, two large tusks (which are detachable and can function as chalk), tiny nostrils, and eyelashes.
Russell is a very dog-like walrus who's loyal to Parker and Russell. She cannot speak, but is more than happy to play with the pair and join their misadventures. She has a magic stomach that functions as a storage place for packages and mail.
- John Trabbic has stated that Russell is actually female, as she has often been confused as a male due to her androgynous appearance and name.
- Russell does not have a voice actor, as she simply makes animal noises.
- In Welcome, Parker says she is a pet, which means she could possibly be the team's pet walrus.