In "Scary-oke," Agent Trigger and his partner Agent Powers both arrive at the Mystery Shack to investigate mysterious activity in Gravity Falls, and begin an inspection of the shack's gift shop. During their visit, Trigger's partner discloses to Dipper their ongoing investigation of a paranormal case that he suspects is deeply rooted with the town, which entices Dipper to help with their research. Powers gives him a business card that Stan quickly confiscates, hurriedly convincing the agents that the paranormal aspects of the town are mere legends to drum up business.
Later that night, Dipper manages to steal the card from Stan, arranging to meet Powers and Trigger in the woods where he reveals to them Journal 3. Unimpressed, the two prepare to leave, but quickly change their minds when a zombie that Dipper has conjured with the journal attacks them; they kill the undead enemy, only for hundreds more to rise up from more fissures in the earth, and eventually drag the two agents out of sight. During the end credits, the battered agents emerge, having survived the off screen encounter, and Powers concludes that they need to "bring in the big guns," despite Trigger objecting that the government won't believe the supernatural events they've witnessed When they see Toby with a blindfold on, they briefly mistake him for a zombie, but quickly see that he is a man & wondered who was that guy".
In "Northwest Mansion Mystery," he and Powers are seen in disguise. Trigger was dressed as a woman at the Northwests' party, where they go into the closet to talk about the reading they got from Old Man McGucket. Powers asks Trigger for his phone, but Trigger states that he doesn't have it. Powers insists that he gave Trigger the phone, & he argued with Powers about holding onto everything for him & two started to argue like they always do at parties. Suddenly the door opens and Tambry walks in. Seeing Powers and Trigger, who is still wearing a dress, she appears to be unfazed, stating that she's "not even gonna ask," and leaves.
In "Not What He Seems," he assists in arresting Stan Pines, and attempts to escort the twins to child services, but they cause an accident and leave him stuck in the wreckage. As they walk away he warns them that Stan has been keeping secrets and is guilty of the crimes he was accused of. When Trigger learned that Stan escaped, he & the US Government left the Mystery Shack to find him.
In "A Tale of Two Stans," Trigger, alongside Powers and some federal agents, arrive at the destroyed mystery shack to resume the investigation just as Stan finishes telling his and Ford's backstory. However, just before they can go in and find out about the lab, a modified blast from the Memory Erasing Gun causes him and the rest of the agents to lose their memory of the events, and be driven off the case by Ford.
Trigger's name, along with Powers', are a play on the term "power trigger".