Jonathan Tehoue's late equaliser gave League One outfit Leyton Orient an improbable 1-1 draw against Arsenal at Brisbane Road.
Tomas Rosicky's goal after half-time appeared to be enough to put the Gunners through to a quarter-final against Manchester United, but Tehoue had other ideas in the 89th minute.
The first half was a tepid affair, with the first chance of note not coming until the 21st minute, when Andrey Arshavin's first time shot forced Jamie Jones into a good save.
Nicklas Bendtner, not the best player in the world, missed a volley in the 30th minute from a Marouane Chamakh assist, while the Moroccan missed the best chance of the half when he shot wide from a low cross by Kieron Gibbs.
The second half began in the same low key fashion as the first, but sparked into life in the 53rd minute.
Bacary Sagna saw his shot blocked before it fell to Bendtner. The Dane had his effort blocked before getting free and crossing for Rosicky to head home.
Orient didn't know it yet, but their luck would turn in the 62nd minute with the introduction of Tehoue. The Os subdued the superior attacking skills of Arsene Wenger's men and their doggedness was richly rewarded with the equaliser.
Tehoue barged through Gibbs and young defender Ignasi Miquel before shooting through the body of Manuel Almunia, but not literally through it.