Striker Matt Smith chose the perfect occasion to score his first goals at Boundary Park as his first-half double helped npower League One Oldham produce an FA Cup upset in beating Liverpool 3-2.
The 23-year-old, who 18 months ago was playing non-league football with Solihull Moors, had the best day of his fragmented professional career after giving the Reds' defence a torrid time.
He scored either side of Luis Suarez's 21st of the season in the first half before Reece Wabara's header put the Latics into the last 16 despite Joe Allen's goal 11 minutes from time.
It was the first time Liverpool had been beaten away from home in the FA Cup by a team at least two divisions below them since defeat at non-league Worcester City in 1959.
Leeds United continued the trend for fourth round upsets in the FA Cup after holding on to beat Tottenham Hotspur 2-1 at Elland Road.
Ross McCormack's goal five minutes into the second half sent Leeds into the last 16 and ensured Spurs befell the same fate as Norwich City and Queens Park Rangers, who were knocked out on Saturday.
Luke Varney had given the Whites a first-half lead and, though Clint Dempsey pulled a goal back, Spurs were unable to find an equaliser as some brilliant last-ditch defending denied Jonathan Obika in the last minute.
Fernando Torres' late goal salvaged Chelsea a replay with Brentford after an enthralling 2-2 draw in their fourth round tie at Griffin Park.
League One Brenford twice took the lead as they threatened a major shock, but cup holders Chelsea responded to keep themselves in the competition.
Marcello Trotta, who is on loan from Fulham gave Brentford a deserved half-time lead only for Oscar to draw Chelsea level with a fine solo effort early in the second half.
Harry Forrester restored Brentford's lead from the penalty spot on 73 minutes after Ross Turnbull brought down Tom Adeyemi.
However, Torres had the final word as his superb curling effort from the edge of the box six minutes from time spared Chelsea's blushes.