It is currently unknown whether or not Moose grew up in Riverdale. There's also nothing known of his home life, such as his family. However, his closest friend appears to be Reggie Mantle, as they are almost always together.
According to Kevin Keller, Moose approached him at the back-to-school semi formal with a proposition, apparently, some time during the discussion, Moose showed Kevin a "certain appendage", one he described as being "horse-like". Following his conversation with Kevin, he spiked the punch bowl and got drunk with Reggie. After the semi formal, he and Kevin headed to Sweetwater River. Despite his desire to engage in sexual acts with another male, Moose insisted that he was not gay. As the two prepare to go skinny-dipping, Kevin stumbles upon the body of Jason Blossom at the shore. 
Moose insists that he be partnered up with Kevin during class, as they have something to talk about. He wanted to arrange another meet up with Kevin on Saturday night. However, Kevin declines as Moose has too many secrets, he then suggested that Moose stick with what he knows best, which is girls. Later that day, in the student lounge, Reggie questioned Moose on what he and Kevin were doing by the river, and why the cops didn't come looking for him, since they found the body. 
Moose, Reggie, and several other members of the Riverdale Bulldogs taunted an anxious Archie, as he got on stage to perform his audition song for the annual Variety Show, the severity of which resulted in the players momentarily appearing in werewolf masks. 
Having learned that Andrews Construction, the company that is owned by Archie's father, was facing great misfortune, Moose, Archie, Jughead and Kevin volunteered to assist him in the SoDale project and keep him on schedule until he could find a real crew. Unlike everyone else, Moose rather enjoyed the hard labor, he preferred working on the construction site instead of the weight room. The day had come to an end as the boys returned to the trailer, but Moose accidentally left his phone back on the project site, as he returned to retrieve it, he stumbled upon two thugs damaging Andrews construction equipment. They then turned their attention to Moose, knocking him to the ground and beating him bloody, before warning him that they'd return if construction for the SoDale project didn't come to an end. Sheriff Keller arrived shortly after to get their statements, while Fred believed the men to be associates of Cliff Blossom, Archie suggested that they could've Southside Serpents, who were angry due to losing their territory.
The next day, with the help of Kevin's boyfriend, Joaquin, who was also a Serpent, Moose, Archie and Kevin infiltrated a known hang out of the Serpents, called the Whyte Wyrm. Once inside, Moose directed his attention towards a patron in the bar that could've potentially been one of his attackers. While the original plan was to find the thugs responsible and call Sheriff Keller, Archie took it upon himself to confront the Serpent, which didn't end well as they were greatly outmanned. Luckily, the fight was brought to an end by FP Jones, the leader of the Serpents and Jughead's father. He removed the boys from the bar, and set them home before they could cause any further trouble. 
A large group of students. Moose included, were led by Cheryl and Chuck as they crashed Jughead's 16th Birthday Party at Archie's house. With a keg over his shoulder, Moose wondered where Archie wanted them, which he replied one in the kitchen and one in the back yard. Then he and Cheryl took the dace floor, where they danced and kissed. He was also there to bear witness to Archie's altercation with Valerie, which he, Chuck and Cheryl had a good laugh about. Unfortunately, the party abruptly came to an end as a fight between Jughead and Chuck resulted in FP sending everyone home.
Moose is an attractive young man with tan skin, hazel eyes, and dark brown hair. He is tall, with an athletic build, due to his place on the football team. He doesn't put much thought into his choice of clothing, typically a jacket or hoodie with jeans.
Like Reggie, Moose embodies several characteristics usually associated with the stereotypical jock. He doesn't appear to be very smart nor does he seem interested in school. Football, and concealing his true sexual orientation are his biggest concerns. Being a closeted gay male, Moose puts all his effort into maintaining this secret, even going as far as having a girlfriend in order to keep up his appearance as the cool and popular jock.
- "Chapter One: The River's Edge"
- "Chapter Two: A Touch of Evil"
- "Chapter Three: Body Double"
- "Chapter Five: Heart of Darkness"
- "Chapter Six: Faster, Pussycats! Kill! Kill!"
- "Chapter Eight: The Outsiders"
- "Chapter Ten: The Lost Weekend"
- See also: Category:Images of Moose Mason
- ↑ Aguirre-Sacasa, Roberto (writer) & Krieger, Lee Toland (director) (January 26, 2017). "Chapter One: The River's Edge". Riverdale. Season 1. Episode 1. The CW.
- ↑ Aguirre-Sacasa, Roberto (writer) & Krieger, Lee Toland (director) (February 2, 2017). "Chapter Two: A Touch of Evil". Riverdale. Season 1. Episode 2. The CW.
- ↑ Lawrence, Yolonda E. (writer) & Krieger, Lee Toland (director) (February 9, 2017). "Chapter Three: Body Double". Riverdale. Season 1. Episode 3. The CW.
- ↑ Maxwell, Ross (writer) & Warn, Jesse (director) (February 23, 2017). "Chapter Five: Heart of Darkness". Riverdale. Season 1. Episode 5. The CW.
- ↑ Williams, Tessa Leigh & Zwart, Nicholas (writers) & Adelson, Steve (director) (March 2, 2017). "Chapter Six: Faster, Pussycats! Kill! Kill!". Riverdale. Season 1. Episode 6. The CW.
- ↑ Cohen, Julia (writer) & Katzenberg, David (director) (March 30, 2017). "Chapter Eight: The Outsiders". Riverdale. Season 1. Episode 8. The CW.
- ↑ Lundin, Britta & Paterson, E. Brian (writers) & Wilkinson, Dawn (director) (April 13, 2017). "Chapter Ten: The Lost Weekend". Riverdale. Season 1. Episode 10. The CW.