The FA Cup may have been short on upsets on Saturday but at Selhurst Park the worlds of Crystal Palace and Leicester City were turned on their heads.
Bruce Dyer scored goals with the ease he generally reserves for missing them as Palace won a home match against Premiership opponents - something they have not achieved in the league all season.
Leicester, who have one of the most reliable rearguards in the country, defended like drains and the usually dependable Matt Elliott made a catalogue of errors.
The key contribution was that of Dyer, whose performance underlined what an enigma he has become. The England Under-21 striker has scored 39 goals in 112 appearances over the last three seasons after joining Palace four years ago from Watford for pounds 1.3m - a record fee at the time for a teenager - but there remains a feeling at Selhurst that he has still to realise fully his potential.
Such a verdict might seem harsh for a player who is still only 22 and has worked hard at his game. Always blessed with great pace, Dyer has added strength and power in recent times and, if his touch still leaves something to be desired, his spirit is unquenchable.
Yet, for all his natural skills and attributes, Dyer has been a source of frustration for successive Palace managers. All too often a devastating turn or burst of speed has been wasted with a careless shot or hurried pass. In particular he frequently chooses the wrong option when his own skills have put him in a dangerous position.
Two almost identical incidents in the last quarter here summed him up perfectly. On both occasions Dyer left defenders for dead with storming runs down the left wing, raced into the penalty area and, with colleagues waiting for a cross on the edge of the six-yard box, wasted the opening by attempting to shoot from an impossible angle.
Not that his team-mates were in any mood to berate him, for by that stage Dyer's hat-trick had put Palace into the fifth round. His first goal was a precise finish from a difficult angle after he had rounded Kasey Keller, his second an instinctive reaction after the ball had flown across the area and his third a cleverly chipped shot into the roof of the net.
Steve Coppell, the Palace manager, said: "The whole game was typical of Bruce. He did some very good things, then the next minute cocked up the simplest things. His nature is his appeal in many ways. Sometimes he has blinkers on and his touch can let him down. But he has a resilience and desire to learn. He's like a sponge. He soaks everything up and comes back for more as he wants to improve."
While this victory may have started to revive uncomfortable memories for Palace - in their last season in the top flight they were relegated despite reaching the semi-finals of both the FA Cup and Coca-Cola Cup - it should also give them hope that they can reverse their home form in the league, particularly if some of the seven first-team players out injured come back soon.
Altough they have failed to win any of their 10 home Premiership fixtures, Palace have now won all four of the other games they have played at Selhurst Park this season - three cup matches and the "away" fixture against Wimbledon.
Palace are short of confidence, however, and until the second goal Leicester were marginally the better team in a closely fought match. Emile Heskey was a handful for a Palace defence in which Valerien Ismael, a club record pounds 2.75m signing from Strasbourg, made a promising debut, but Leicester's finishing was poor and Kevin Miller's shot-stopping was outstanding.
Leicester might still have got something out of the game but for an uncharacteristic display by Elliott, whose slack defending played a part in all three goals. "I told Matt he may as well have sat on the bench this afternoon," Martin O'Neill, the Leicester manager, said. "But it was his worst game for a long time and he's been absolutely brilliant for us until now."
Goals: Dyer (33) 1-0; Dyer (62) 2-0; Dyer (66) 3-0.
Crystal Palace (5-3-2): Miller; Smith, Ismael, Linighan, Hreidarsson, Gordon; Edworthy, Roberts, Fullarton; Dyer, Brolin. Substitutes not used: Quinn, Boxall, Ginty, Martin, Nash (gk).
Leicester City (3-5-2): Keller; Kamark (Cottee, 70), Elliott, Walsh; Savage, Lennon, Parker, Izzet, Guppy; Heskey, Marshall (Wilson, 80). Substitutes not used: Prior, Fenton, Arphexad (gk).
Referee: P E Alcock (Halstead, Kent).
Bookings: Palace: Ismael. Leicester: Izzet, Lennon.
Man of the match: Dyer.