Forest, who had slipped to 11th place after taking only four points from their previous five matches, were the latest side to make a mockery of the form book in the Championship after Sharp converted a late first-half penalty to cancel out Paul Green's early opener for Leeds.
Sharp fired his second of the game soon after the restart and a three-goal blitz in nine minutes - Rodolph Austin scored a clumsy own goal and Dexter Blackstock headed home the fourth - stunned the visitors, who had celebrated the completion of last week's takeover by Dubai investment bank GFH Capital with victory over Middlesbrough on Saturday - Leeds' fifth win in their last six league games.
Defender Greg Halford, midfield pair Radoslaw Majewski and Adlene Guedioura, plus striker Blackstock returned for Forest, while Leeds, for whom Davide Somma struck a late second, recalled Adam Drury and midfielders Michael Brown and Austin.
The game was only 12 minutes old when Leeds nosed themselves ahead. Jerome Thomas swung the ball over from the left and after El-Hadji Diouf's shot was parried by Forest goalkeeper Lee Camp, the ball broke for Green to tap home into an unguarded net from no more than two yards.
It was midfielder Green's third goal in four league games and Leeds, who won the corresponding fixture 4-0 just over a year ago, were next to threaten again when Jamaica international Austin, back after a nine-game lay-off due to an ankle injury, drilled a 25-yard shot over the crossbar.
Leeds striker Luciano Becchio's header from Drury's cross was comfortably gathered by Camp, while at the other end visiting goalkeeper Paddy Kenny pulled off a fine save in the 28th minute to keep out Forest defender Elliott Ward's goalbound header.
Forest deservedly equalised in the 44th minute. Referee Lee Probert did not hesitate in pointing to the spot following Lees' challenge on Sharp and the Forest striker picked himself up to send Kenny the wrong way with the subsequent penalty for his eighth goal of the season.
Forest, suitably perked, looked the more dangerous side after the break and stole into a two-goal lead within 12 minutes of the restart.
Blackstock headed a long clearance brilliantly into the path of Sharp, who coolly rounded goalkeeper Kenny and rammed home his second goal in the 54th minute and three minutes later an out-of-touch Austin swung a clumsy leg at Forest defender Ward's cut back and lashed the ball into the roof of his own net.
Worse was to come for Leeds. Forest midfielder Andy Reid ghosted passed right-back Sam Byram and clipped in a fine cross for Blackstock to shrug off Tate's challenge and head powerfully beyond Kenny into the bottom corner.
Leeds substitute Somma made his second appearance in 19 months midway through the second half following a serious knee injury and slid home Ross McCormack's cross from close range to reduce the deficit in the last minute, but not before Kenny had pulled off another fine save to tip away Forest defender Alan Hutton's 30-yard blockbuster.