The Bird Nest Worm is a pink earthworm that appears in the Season 5 episode "BMO Lost." After BMO is carried off by a giant pink bird, BMO quietly crawls out of the nest and onto the edge of the steep cliff that the bird's nest is perched on. Just as it begins to take its first step, however, the Bird Nest Worm springs out of the side of the nest yelling that it isn't safe out there and that BMO is more than welcome to hide in there. This startles BMO, causing it to tumble down the ledge, where BMO then meets Bubble. Seeing his mistake, the Bird Nest Worm sighs and says, "Oh, shoot, man. Uh-oh." The worm was clearly only trying to help, but due to his spastic nature, he misses an opportunity to find company.
The Bird Nest Worm bears a resemblance to Shelby, another earthworm who lives inside of Jake's viola. However, the Bird Nest Worm is different in that it has six visible segments below the clitellum, whereas Shelby has none. Additionally, Shelby's eyes are simple dots, whereas the Bird Nest Worm's eyes are reminiscent of those of Jake the Dog.
Hey, man, it's safe in here! You can hide in here! [This causes BMO to tumble off the edge.] Oh, shoot, man. Uh-oh.