A Hopeless Wound
From Weavered.com
Abby is one naughty nurse.
Romano returns Elizabeth's wedding ring.
Corday supervises Nathan, the oldest newest medical student at County on surgical rotation. He has Parkinson's.
Weaver indentifies with an woman in her 40's who is having pregnancy complications.
Kovac lets his personal problems affect his work.

From Epnebelle:
Episode 9.5
"A HOPELESS WOUND"
It's Halloween. Ella's a cow, Carter's a skeleton, and Abby's a "Naughty Nurse". Use your imagination.
Romano returns to work and hovers too close for Elizabeth's liking.
Elizabeth supervises a new flock of med students, including Paul Nathan, who's confident, great with patients and has Parkinson's.
The staff treats a woman and her baby after a homebirth gone bad.
An apartment building fire brings burn patients once more - in various costumes.
Luka acts like an ass to everybody.

Dialog spoiler from weavered.com:
ABBY:He got my boobs, but my heart belongs to you, boney boy."
CARTER: "Yeah, I'll give you a bone, nasty nurse."

From Ain't It Cool News:
Halloween falls on the first day of sweeps this season, and we've gotten a big chunk of “ER’s” Oct. 31 Halloween installment, titled “A Hopeless Wound.”

* The episode introduces Don Cheadle as Paul Nathan, a middle-aged med student suffering with Parkinson’s. He impresses everybody, including Romano, when he spots a misdiagnosis of necrotizing fascitis. We learn that Nathan was, until recently, a successful commodities trader.

* Ella goes trick-or-treating as a cow.

* Rocket Romano gets some bad news regarding the fine motor skills of his reattached arm. We seem him highly frustrated at having to just lend advice to slower and less talented surgeons.

* County finds itself contending with a Halloween-night apartment fire that sweeps through a gay costume party. Dozens of homosexuals find their bodies fused to their jungle-girl, Cher, and Streisand outfits. Pratt gets fairly creeped out by the flood of half-charred drag queens.

* Kovac cheeses off Chuny by almost laughing when a horny patient puts the grab on her hinder. Kovac gets in more serious trouble with Weaver later in the show after he convinces a distraught mother to sign a DNR order for her doomed newborn, who suffers from a deadly genetic defect. (This whole storyline should prove another enormous ER tearjerker.)

* John and Abby agree to spend their entire shift together in costume. Abby turns up as a “naughty nurse,” while John arrives in a skeleton outfit. At shifts end, Abby gives her falsies to the horny patient, but tells Carter, “He got my boobs, but my heart belongs to you, boney-boy.”

From the scavenger hunt at weavered.com:
Carter is treating Woody, a homeless drunk patient, towards the end of his shift. Abby comes to talk to him and Woody tells her that she's the most beautiful nurse in the hospital and asks to play with her breasts as his 'dying' wish. Carter is slightly annoyed, but Abby pulls out two 4x4's and hand them to Woody and tells him to knock himself out. As Carter and Abby walk away together, he jokes that she puts its out for just anybody. And then come the lines about "you have my heart" and "I'll give you a bone, nasty nurse." She corrects him that it's "naughty" nurse and that nasty nurses are the naughty ones that get diseases and Carter jokes that it happens when you go around letting people play with your boobs.