Spot-kick king and hat-trick hero Liam Lawrence clinched a thrilling last-gasp win and a third round home tie with Burnley for lowly Mansfield, to leave Tony Adams still looking for his first win in charge at second division Wycombe.
Lawrence calmly struck the winner from the penalty spot with the last kick of the game three minutes into injury time after Roger Johnson felled Lee Williamson.
It was Lawrence's eighth successful penalty of the season and came 18 minutes after he had hauled the Stags level with another spot-kick after keeper Steve Williams brought down substitute Iyseden Christie.
Mansfield's thrilling comeback wiped out an amazing fightback from Wycombe, who had turned round a half-time deficit to lead their third division hosts through two Jermaine McSporran goals inside three minutes.
Earlier Wycombe had survived two early scares before Lawrence fired the first of his treble in the 14th minute expertly lobbing the keeper from just ten yards at the second attempt.
A minute later Wayne Corden's fierce drive was deflected narrowly wide as Wycombe struggled to get out of their own half.
After a scrappy 25 minutes Corden again went close with another long-range strike which Williams fumbled before saving at the second attempt.
That sparked a frantic spell of pressure from the third division side.
Junior Mendes, Craig Disley, Tom Curtis and Corden all had goalbound shots blocked and then Corden's dipping drive was tipped on to the post by the back-pedalling keeper.
It took the second division side until the 49th minute to test keeper Kevin Pilkington with a shot, Johnson's low drive comfortably saved.
Two minutes later Stuart Roberts blazed over after a mazy run across the penalty area.
McSporran made no mistake however with two goals in three minutes to turn the tie around.
In the 56th minute Craig Faulconbridge pounced on a David Artell error to create the chance for the small striker, who then raced clear three minutes later to convert an Ian Simpemba pass.
That double sparked the tie into life and set up the thrilling finale.