Alastair Cook stole most of the headlines on day three of the Boxing Day test as England subjected Australia to a miserable day in the field - but then Usman Khawaja appeared to claim an incredibly controversial catch in the final half hour of play.
Cook's fifth double-ton snapped a series of records and helped spur England to 491-9 at stumps.
The former skipper even leapfrogged test legend Brian Lara into outright sixth on the list of test cricket's most prolific run scorers.
The series erupted, however, when Stuart Broad skied a Pat Cummins short ball out to deep mid-wicket, but a video referral from the on-field umpires completely divided commentators.
Khawaja dived forward to take the catch, but the replays were inconclusive.
A decision by the on-field umpires to send the decision up to the video umpire, proved to be the reason Broad was sent packing.
The video replays showed Khawaja took control of the ball when he got his fingers under the ball while diving forwards.
However, as he skidded forward, the ball bobbled up out of Khawaja's hands.
From there the camera angles lost sight of the ball as Khawaja appeared to re-gain possession by sandwiching the Kookaburra between his forearm and guts while rolling forward.
He got up celebrating, but then motioned to the on-field umpires that he was unsure.
This admission still resulted in umpires sending the decision to video umpire Joel Wilson with the advice that the on-field decision was that Khawaja successfully clunked the catch.
Broad was sent back to the pavilion for a pyrotechnic 56 runs from 63 balls.
Khawaja's ugly diving catch quickly became one of the biggest flashpoints of the series.
"That is an incredible decision," English great Graeme Swann told the BBC.
"If you are English you see that and think there is no way that is out. If you Australian you say that is definitely out."
Michael Clarke told Channel 9 there was too much doubt for the umpires to make any recommendation to the video official.
"I don't know how he would know that," Clarke said of Khawaja's initial reaction to claim the catch.
"He is all over the place. I'm not saying he is trying to cheat or anything, but the ball was going all over the place and diving forward.
"Certainly, I think if there is any doubt, must go the batsman's way. You can't guess."
Earlier, Broad raced to fifty from just 59 balls as Australia's short-ball barrage leaked runs.
Broad's boundary from a pull shot off the bowling of Pat Cummins also brought up the 100-run partnership between Broad and Cook for England's ninth wicket after the Ashes villain walked to the crease at 373-8.
Cook will resume at the crease not out on 244 alongside James Anderson, who is yet to score from 15 balls at the crease.
He was dropped by Steve Smith twice as he helped England to a lead of 164 runs.
Cook, who had struggled severely as Australia eased to an unassailable 3-0 lead in the series, posted the highest test score by a visiting batsman at the MCG and his highest score against Australia.
He is also on the cusp of becoming the first Englishman to carry his bat in a test since Mike Atherton in 1997, while it would be the first time an opener from either nation has achieved the feat in an Ashes Test since 1979.
Australian captain Smith, struggling with a stomach bug, failed to stop the tourists' tail from wagging for the first time this summer.
England slipped to 307-6 after both Jonny Bairstow (22) and Moeen Ali (20) fell playing loose strokes to Nathan Lyon.
Cook combined with Chris Woakes in a 59-run stand then batted with Broad for just the second time in 113 tests.
Cook and Broad, who both started the game under pressure to retain their spot in the XI, hammered home England's advantage.
England's No 11 batsman Anderson survived 25 minutes at the crease, further demoralising the hosts.