Dipper and Mabel spend several hours trying to get the creature out of their bedroom closet at night, recording the whole process on camera. Mabel remains unconvinced it's anything more than a possum. Before the camera's batteries can totally die, they decide to open the closet door. Thing 26 bursts out of the closet with fangs bared and the twins scream as the camera loses power completely. In the last few seconds, Mabel can be heard screaming: "It's not a possum! It's not a possum!"
Presumably later, Dipper sends a postcard to his parents that includes a picture of the beast, and asks them to send help and/or weapons. It is shown once again as an enemy in the flash game Fright Night, on the show's website.
The creature is a short, rotund, yellow-orange creature with large white eyes with pinkish-red pupils, fangs, and short, stubby legs. It's only other distinguishing feature is a small patch of black hairs on top of its head.