Bert Tyrannosaurus Macklin is the alter-ego of Andy Dwyer. Andy goes into character as Bert when a situation requires the presence of law enforcement. He has a brother named Kip Hackman.
Andy is first shown in the character of Bert Macklin in "Greg Pikitis", while questioning local teen Greg Pikitis on his vandalism of Mayor Percy's statue. Bert waltzes in, claiming to work for the Federal Bureau of Investigation (FBI). However, Greg is mean to Bert and makes him cry.
In "Ron & Tammy: Part 2", Andy writes a fake email, signed 'Bert Macklin', to get April out of working for Chris.
In "Born & Raised", Bert assists Leslie in retrieving her long-form birth certificate from the Wamapoke County Records by storming the back of the records office after the employee working there tells her it will take a few weeks to get her birth certificate to her.
Bert is on high alert in "Bus Tour" after someone tries to throw a pie at Leslie at a campaign rally. He uses Jerry as a case study to try and determine the angle at which the pie was thrown towards Leslie. Bert eventually solves the pie case: it was meant for Ben, not Leslie, and it was thrown by Joe Fantringham, whom Ben had fired. Andy catches Joe attempting another pie throw, but he forgets to actually stop him and Ben is hit in the face.
In "Pawnee Commons", April roleplays as Judy Hitler and Andy as Bert Macklin. However, when Bert Macklin makes a child cry and Andy Dwyer helps him find his mother, April suggests that Macklin retire, which he does, making this one of his final appearances as Andy's alterego, although he returned as a character in The Johnny Karate Super Awesome Musical Explosion Show. However, Macklin comes out of retirement in Are you better off? to solve the mystery of who was pregnant.
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In "The Johnny Karate Super Awesome Musical Explosion Show", he is a character. The show ended in the eponymous episode. Bert Macklin appeared again once more in "One Last Ride", in April and Andy's flash-forward to 2022, when Andy Dwyer dressed up as him for Halloween, role-playing with April, who was dressed as Janet Snakehole.