Aberdeen suffered a hugely embarrassing Scottish League Cup exit to Second Division strugglers East Fife on penalties after an action-packed match had finished 3-3 after extra time.
The Dons, who have made a habit of exiting cup competitions to lower league sides in recent seasons, ran out 6-0 winners when the sides met in the Scottish Cup in January but this proved to be a much closer affair.
An upset looked on the cards when the part-timers, currently bottom of the Second Division, broke the deadlock when Ryan Wallace smashed the ball home after 31 minutes. Rory McArdle headed home an equaliser five minutes before half-time and Darren Mackie gave the Dons the lead two minutes after the break.
Two goals in as many minutes from Matthew Park and Robert Sloan gave the Fifers the initiative, but Fallon forced the game into extra time when he netted from the spot after Mohamed Chalali had been brought down by Steven Hislop.
When extra time finished goalless, it was the Fifers who kept their nerve in the penalty shoot-out, with Chris Clark missing the decisive spot-kick for the Dons.
Hibernian booked their place in the quarter-finals with a penalty shoot-out victory at Motherwell. The sides were locked at 2-2 after 90 minutes following Garry O'Connor's late equaliser, and were unable to add to the score in goalless extra-time.
Visiting goalkeeper Mark Brown saved from Jamie Murphy and then decisively from Nicky Law in sudden death, after home counterpart Darren Randolph had also saved a spot-kick from Callum Booth.
Jim Goodwin's super strike helped St Mirren book a quarter-final place at the expense of St Johnstone at McDiarmid Park. The Buddies, beaten finalists in the competition in 2010, impressively ended a 14-game winless record against their opponents stretching back to August 2005.
Jamie Adams put through his own net before Goodwin's excellent finish - his first for the Paisley men - gave Danny Lennon's side a deserved half-time advantage they never looked in danger of losing.
A Paul Heffernan hat-trick helped Kilmarnock to a 5-0 win over Queen of the South. Gary Harkins opened the scoring after just two minutes, his deflected shot nestling in the corner of the net. From that moment onwards Heffernan was to make the headlines.
The Queens defence were patently unable to cope with his movement, as a ruthlessly clinical display took his tally for the season to a remarkable eight goals in six games. Substitute Ben Hutchinson added some deserved gloss to the score, curling a delightful left-footed effort past a shell-shocked Lee Robinson.
Dundee United moved into the quarter-finals but were made to work for their 2-0 victory over Airdrie United. Ryan Dow scored his first goal for the club on 11 minutes after Paul McKane had failed to hold a Stuart Armstrong shot.
Ryan Donnelly missed Airdrie's best chance when he failed to find the net after rounding Dusan Pernis midway through the first half, and John Daly finished the tie when he slotted home Paul Dixon's cross 15 minutes from time.