OZ is a fictitious artificial mutagen responsible for the creation of the Ultimate Marvel Universe's Spider-Man, and many other characters.
The OZ formula was created previous to Ultimate Spider-Man #1 by Norman Osborn, or, more precisely, OsCorp Industries. The formula created to reproduce the Super Soldier drug for S.H.I.E.L.D., although it had yet to be perfected. Despite this, Norman Osborn was garnering much interest in OZ, while not revealing what it actually was. The company appeared to be prosperous, but was failing due to Osborn's hastily announcing the "miracle drug OZ" without being able to release it due to its unfinished status. As of Ultimate Spider-Man #1 animal testing had begun, with the Spider No.00 showing "interesting developments". This same spider is misplaced as Osborn is distracted by a phone call.
While on a science field trip to Osborn Industries Norman Osborn's son Harry Osborn's friend Peter Parker is bitten by the escaped spider No.00, and passes out after vomiting. He later passes out at school and taken to the hospital. Here his blood is taken, but swapped out by Osborn's henchman. This leads Norman Osborn's head scientist Otto Octavius to conclude, after some tests, that the OZ is killing him. Osborn decides that "he's going to die anyway" and arranges for him to be killed by his henchman Shaw instead. He is unsuccessful due to Peter Parker's emerging powers. The effects of the OZ treated spider venom manifest as:
This leads Osborn to hypothesise that the OZ gave him the enhanced abilities of a spider, then a serum of his own blood in an OZ solution would give him the enhanced abilities of himself. He then plans to reproduce the accident in experimental conditions.
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