Irish Cup holders Glenavon were 2-0 down at half-time but fought back to beat Championship Two side Moyola Park in the fifth round game at Mill Meadow.
A huge upset looked on when underdogs Moyola scored before the break through Darren Walls and Chris Dowie.
Kevin Braniff pulled a goal back early in the second half and it was 2-2 whe the same player's header was deflected in by a home defender.
Eoin Bradley headed in a a late winner for the senior side.
Things were not so fraught for Premiership champions Cliftonville who saw off Ards Rangers of the Amateur League 6-0 at Solitude.
Joe Gormley and Jay Donnelly had the Reds 2-0 up at the break and they both scored again in the second half along with David McDaid and Martin Murray.
McDaid and Steven Hislop of Ards Rangers were sent-off.
Ballymena, last season's beaten finalists, were 4-0 winners over Crumlin Star of the Amateur League.
Matt Tipton netted the first with an early penalty and Gary McCutcheon struck the second before the interval.
Darren Boyce scored twice in the second half while Crumlin's skipper Paul Berne was sent-off for a foul on United's Allan Jenkins.
The all-Premiership clash between Dungannon Swifts and Ballinamallard United was the only tie to go to extra-time.
Gary Liggett scored the goals which took the Swifts through 4-2 at Stangmore Park.
In the other game between tip flight sides, Warrenpoint Town pulled off a 3-1 win away to Coleraine.
Daniel Hughes for the first and Stephen Hughes the other two although both had earlier failed to convert penalties.
Premiership leaders Crusaders romped to an easy 6-0 win over their Seaview tenants Newington YC.
Richard Clarke, Timmy Adamson, Barry Molloy, Diarmuid O'Carroll (2) and Stephen O'Flynn were on target against the team from Championship Two.
Glentoran booked their place in the last 16 by beating Ards 2-0 at the Oval thanks to goals scored by Danny McKee and Fra McCaffrey.
|Irish Cup fifth round results|
|Annagh United||1-3||Ballyclare Comrades|
|Ballymena United||4-0||Crumlin Star|
|Dungannon Swifts||4-2 after extra time||Ballinamallard United|
|H&W Welders||2-0||Derriaghy CC|
|PSNI||1-2 after extra time||Portadown|
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