Mason Brown, (original version: Bruce Brown (ブルース・ブラウン Burusu Buraun)) is a Subterra brawler from Gundalia, and part of the Gundalian Agents. He seems to be the most calm person of the team when it come to a battle, but when it comes to anything else he freaks out and blames Avior. He also calls his partner "old timer" or "old dog" in many of the episodes.
Mason is a rather big showoff who holds no loyalty towards Barodius, and is instead loyal to the Gundalian Elder Nurzak. He escapes the fate met by Lena, Jesse, and Zenet by escaping Kazarina's ship before he could be caught with failure. Though he is a Gundalian, he has a respect for Fabia Sheen and was amazed by Aranaut and Lumagrowl's level 2 Battle Gear abilities.
He is shown to be friends with his teammates Ren and Jesse, and does not hold a grudge against Jake despite his defeat at Jake's hands. However, he and Avior don't seem to get along and constantly argue with each other; Avior thinks Mason is a smart aleck, while Mason finds Avior naggy.
In Brawler to Be, he battles an unnamed kid with a Raptorix and wins. Then, Dan challenges him to a battle, but Jake steps in and wants to prove himself. He defeats Jake in the first round, but loses in a rematch.
In Confrontation, he and Lena lost to two top-ranked players while using their non-Guardian Bakugan to test their strength. The kids were then brought back to the Twelve Orders and hypnotized by Kazarina in order to recruit them.
In Hostile Takeover, he faces Dan Kuso and Shun Kazami in a tag brawl with Taylor (a brainwashed kid). He lost this battle, even after using his Battle Gear. Later, he and the rest of Ren's team, save for Sid, are chewed out in The Sacred Orb for their failure to recruit the Battle Brawlers to their side against Neathia.
In Decoy Unit, he reveals his actual form and is given a second chance by Airzel against Marucho and Jake. The battle ended in a tie after Marucho and Jake fled the battle using Akwimos's last ability, which froze Avior and Strikeflier and distracted the Gundalians.
In The Secret of the Orb, Mason heads off with Kazarina, who was sent off with Nurzak on a reconnaissance mission. However, Mason escapes after striking down two Gundalian guards. He then heads off to Neathia, possibly to switch sides, but falls into a large crack in the ground when the Sacred Orb gets "angry" and starts shattering everything. Although Avior saves him from falling, both are sent around the dimensions when the Sacred Orb gave off a massive energy surge.
In Genesis, Mason and Avior are seen stuck in between dimensions along with Nurzak and Sabator. After Dan defeats Dragonoid Colossus, he is brought to Neathia along with Nurzak and joined the Brawlers as they travel to Gundalia. He changes back into his human form again.
In Infiltrated, he, Ren, Nurzak, and Fabia split off from the rest of the Brawlers to rescue his former teammates, Lena, Jesse, and Zenet. Later, he and Ren split off into another group to rescue his teammates while Nurzak and Fabia battled Kazarina and Stoica.
In Final Strike, he leaves the Brawlers to look for Nurzak, who he still believes is still alive. At the end of the episode, he is seen continuing his search for evidence of Nurzak. He finds Nurzak in Gundalian Showdown, just in time to help Fabia defeat Kazarina. Even though he ends up only watching Fabia and Nurzak battle, he continues to observe the battle in Broken Spell.
In Code Eve (episode), he, Fabia, and Nurzak rush to Nurzak's ship to return to Neathia and help the Brawlers fight Barodius. On the way, they are stopped by Gill and Fabia and Mason fight him in order to buy Nurzak time to start up the ship. After they return to Neathia, Mason reunites with his teammates.
In Destiny Revealed, he reunites with his former teammates on Neathia, but is easily defeated by Phantom Dharak when they try to attack Barodius. After Dan emerges victorious against Barodius, the Gundalians return to their homeland.
Mason made his only appearance in an image, trying to defend Gundalia from the Chaos Bakugan with Avior.
- He shares his surname with Joe, though they are not related.
- He tends to spazz out when things don't go his way (much like Shadow) as he blamed Avior when he lost to Jake and started laughing for no reason when he discovered he was walking in circles.
- He and Nurzak, both of who are Subterra brawlers, joined the Battle Brawlers in Episode 29.
- He is the third Gundalian to join the Battle Brawlers, after Nurzak and Ren.
- Dan said both Mason and Nurzak were sent between dimensions by Barodius. While this is true for Nurzak, this is not entirely true for Mason, who was accidentally sent by the Orb.
- In episode 36, it was shown that Mason may like Fabia, because he was flirting with her when he arrived with Nurzak, and Avior told him, "Quit flirting, we are here to settle a score". Also, in another episode, he commented about the level 3 Battle Gear ability she used, prompting Avior to ask that if he was jealous.
- His human form seems to be less bulky than his Gundalian form; when he transforms from Gundalian to Human form, his chest and arm muscles get smaller.
- He is the only member of the Gundalian Agents (excluding Ren) to escape punishment from a Major Twelve Order.
Mason is shown to be a skilled brawler, only losing three times against the Brawlers, one of which was on purpose.
Bakugan: Gundalian Invaders
|Unknown Ventus Brawler||4||Win|
|Unknown Darkus & Subterra Brawlers (Tag with Lena)||5||Lose (Deliberate)|
|Casey & Taylor (Tag with Sid)||8||Win|
|Dan Kuso & Shun Kazami (Tag with Taylor)||8||Lose|
|Jake Vallory & Marucho Marukura (Tag with Airzel)||15||Draw|
|Gill (Tag with Fabia)||38||No Outcome|
Bakugan: Mechtanium Surge
|Chaos Bakugan Army (Tag with Jesse)||18||No Outcome|