ER Clip Summaries, from "Fear of Commitment"

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Clip 1: Two mascot-suited people are brought into the ward, introducing the characters, one in a possum suit and the other in a kangaroo suit. One refuses to use his real name, going by "O. Possum" instead.

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Clip 2: It is revealed that the two mascots were not from a sports event altercation as assumed by the doctors, but were "furries" at a convention called "FURTurama". One "furry fan" in an opossum costume was "scritching" the guy in the kangaroo costume. The kangaroo (apparently modeled after a "Burned Fur" architype) informs the doctors that the possum guy reached into the kangaroo guy's pouch, so the kangaroo guy decked the possum, after which the possum guy bit the kangaroo guy in return. The kangaroo fur-suiter denotes sternly that "I'm not into the weird stuff."

Clip 3: The kangaroo fursuiter explains the liberation he feels from fur-suiting (which is more or less what "Furries" are equated with in this generalized depiction). Realizing how odd this must sound to the doctors, he adds, "At least I'm not a plushie or furvert..." and explains the two as "people who are overly fond of plush animals" and "people who have sex in their costumes" respectively; "I just like the suit. Some people think its wrong, but I'm never happier than when I'm a kangaroo."

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Clip 4: In the final end gag, the doctor, who has been given a cat hand puppet called "Mr. Whiskers" by a homeless lady who was a children's show host, discovers the puppet in an under-the-sheets rendezvous with O. Possum. Ouch.