Bottom of the table Wimbledon secured only their fifth league win of the season and ended a run of four straight defeats as they landed a knockout blow on Boxing Day.
Teenagers Wade Small and Dean Lewington scored their first-ever senior goals as the lively Dons raced into a 2-0 first-half lead.
And midfielder Jobi McAnuff blasted a stunning late third to inflict a third successive 3-0 defeat on Reading and leave Steve Coppell's play-off hopes in tatters.
Small drew first blood on nine minutes, scoring his first for the club after neatly controlling and turning home a cross from Dons captain Nigel Reo-Coker.
Reo-Coker's work down the right had set the tone for the afternoon as his trickery left defender Ivar Ingimarsson stranded and his cross had the rest of the Reading defence looking on as Small fired home.
Ingimarsson nearly made up for that woeful defending with a towering header from a Scott Murray corner at the other end, but his effort flew straight at Dons keeper Steve Banks.
Instead, it was Wimbledon who surprisingly dictated play.
Adam Nowland should have scored a second when Steve Sidwell presented him with the ball right in front of goal, but the Dons midfielder shot wide with only goalkeeper Marcus Hahnemann to beat.
But Nowland redeemed himself on 23 minutes with a perfectly flighted free-kick to pick out the run of Lewington, who flicked a header beyond Hahnemann.
Reading rarely looked like cutting back that deficit, though substitute Lloyd Owusu, making his debut after joining on loan from Sheffield Wednesday, did strike a post with a late header.
Nicky Forster was denied by a brave Banks save after Sidwell had sent him clear, but any improvement on the scoreline would have flattered Reading.
Instead, Wimbledon turned the knife with a stunning second.
McAnuff cut inside from the right wing and saw two shots blocked before hitting an unstoppable left-foot shot beyond Hahnemann and into the top right-hand corner.
The remarkable win still leaves Wimbledon stuck at the bottom of the table, but offers the chance of some New Year hope for their long-suffering fans.