As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GNDED. ON TAXI OUT WITH ONLY NR 1 ENG RUNNING, REPORT OF SMOKE IN AFT GALLEY & RETURNED TO GATE. FOUND A GREEN HYD SYS ELBOW FITTING LEAKING ONTO THE APU BLEED AIR DUCT RESULTING IN SMOKE & AN ODOR. THE CRACKED ELBOW WAS REPLACED & LEAK CHECK IAW AMM 20-23-11. NO ADDITIONAL ODORS WERE NOTED.