Pre-Digimon Mighty Squadron
Brick & Stick probably attended the same elementary school as the kids who would later become the DigiDestined. Before the events that happened in the first season, it is revealed that they became best friends after the incident where Brick decided to not beat up Stick for shoving a popsicle down his shirt.
Digimon Mighty Squadron
Brick & Stick start out as bullies at Tokyo Junior High School & often hang out at the Youth Center & Juice Bar. Their actions are motivated by greed & ego in the first seasons. Wacky schemes abound, always ending with their failure & humiliation.
In the episode DigiDestined With Evil Part IV: Eclipsing DinoOmnimon, Brick & Stick are trying to escape in an abandoned bus when they are captured by a giant sized MadLeomon. However, just as the Claymon are about to push the bus with Brick & Stick in it off a cliff, the DigiDestined form DinoOmnimon & help Brick & Stick to safety before engaging in a fierce battle against MadLeomon, Minervamon, & a giant-sized Alexander.
During the second season they attempt to discover the secret identities of the DigiDestined & repeatedly fail. Ironically enough, they do discover the DigiDestined's identities twice: once they save the DigiDestined when they lose their memories & lose their Digimon in front of them; Brick & Stick trick the evil Digimon to fire his amnesia beam through a prism, distorting the beam & restoring the DigiDestined's memories. Unfortunately Brick & Stick lose their short-term memories in the process due to being flung back by the amnesia beam & landing on their heads. The second time a psychic points the DigiDestined teens out to Brick, but he doesn't believe her as they are holding a picture of the DigiDestined's Digimon at the time just given to them by Hojo.
A popular change of direction for the duo occurrs in the third season of Digimon Mighty Squadron when they join the Tokyo Junior Police Force (in an attempt to impress women, due to their belief that women love men in uniforms) & first meet Lieutenant Yuuji. Lt. Yuuji becomes a permanent character himself, frequently giving Brick & Stick orders that they fail to perform, leading eventually to his anger (rather than their humiliation). Despite this, Brick & Stick are close to Lt. Yuuji.
During Digimon Zeo, Brick & Stick remain members of the Junior Police Force until they accidentally cause Lt. Yuuji to be fired by the police chief. They quit the force & join Yuuji when he opens his own detective agency, but walk out on the agency to take an undercover mission in France, the details of which are never disclosed.
During this time, Brick & Stick secretly host SkullSatamon & MadLeomon, two villains who lose their memories after the attack at the end of Digimon Mighty Squadron.
At the start of Digimon Turbo, the gap between Good as Gold & Turbo: A Digimon Movie reveals that Brick & Stick had returned from France & reconciled with Stone. All three eventually got a chance to rejoin the Police Force (which, like many of the holes in the season, is never fully explained) before Lt. Yuuji goes to replace Hojo as owner of the Gym & Juice Bar. Unfortunately before they can get back to work, they are transformed into chimpanzees by Boogeymon.
Brick & Stick remain chimpanzees for several episodes. Lt. Yuuji takes the chimpanzees into his care (claiming that they seem 'familiar'), & they make several attempts to inform him of their true identities.
They are eventually transformed back into humans, but a temporary side-affect renders them invisible. This state only lasts for a few episodes before they finally return to normal & attempt to take on proper jobs (Lt. Yuuji arranges for them to get a new one most episodes).