What happened to the “Cockamouse” after it terrorized Marshall and Lily in How I Met Your Mother season 1? The creature lived in their apartment but the couple had trouble identifying the species. The Cockamouse was later thrown out of the apartment, although that wouldn’t be its last appearance in the series.
The Cockamouse was introduced in the season 1 episode, “Matchmaker.” Lily (Alyson Hannigan) spotted a peculiar creature roaming around the apartment so she ran down to MacLaren’s to tell the rest of the gang. She thought it was a cockroach but when Marshall (Jason Segel) investigated, he deemed it to be a mouse. They negotiated with the name, “Cockamouse.” They tried to kill the Cockamouse with a phone book before they got a good look at the creature. It was then described as having six legs, an antennae, an exoskeleton with some fur, as well as whiskers and a tail.
Marshall eventually caught the Cockamouse and took it to Columbia University Biology department. When he presented the creature to the staff, the cage was empty, meaning the Cockamouse was still loose in the apartment. It was then that Robin (Cobie Smulders), the skeptic, finally realized that the creature existed. She and Lily ran from the Cockamouse before Marshall returned home, grabbed it, and threw it out the window. The group assumed the Cockamouse was dead but then its wings emerged and it tried to fly back into the window. That was just the beginning of the Cockamouse’s history in How I Met Your Mother.
In How I Met Your Mother season 5, the Cockamouse made a return in the episode titled “Home Wreckers.” Ted (Josh Radnor) had recently purchased an old dilapidated house and the Cockmouse could be seen running across the floor. The following season, a newspaper was shown with an article that was headlined: “Does the Half-Roach Half-Mouse Really Exist?”
The legend of the Cockamouse continued to grow in late season 6 during the episode “The Perfect Cocktail.” Ted and Zoey (Jennifer Morrison) spent the night at The Arcadian where the infamous creature appeared. Ted referred to the Cockamous as an old friend and learned that it now had babies, meaning there were more Cockamice out there.
How I Met Your Mother ended in 2014 with season 9. The final season tied up many loose ends and it also paid homage to a few long-running gags. During the series finale episode, the Cockamouse made one final appearance by running out in front of Marshall and Lily. The creature still terrified them, even though nearly a decade had passed. The Cockamouse cameo felt like a full-circle moment for How I Met Your Mother, and there’s no question why the creature holds a special place in the minds of viewers.
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