The Reds left it late to secure a place in the fourth-round draw by forcing a replay just when the Hammers were poised to celebrate victory.
Obviously, it wasn't the first time that United have scored late on to stay in the competition so we took a look back at some instances in the past when a goal in the final 10 minutes has avoided being beaten in the world's most famous cup tournament.
2002: Aston Villa 2 United 3
2-0 down with 13 minutes left, the Reds roared back with Ruud van Nistelrooy scoring twice past Peter Schmeichel in quick succession to add to Ole Gunnar Solskjaer's equaliser. Some away fans invaded the pitch to mob the deadly Dutchman.
1999: United 2 Liverpool 1
Another tie in which victory was snatched from the jaws of defeat. Dwight Yorke levelled Michael Owen's opener with a couple of minutes left before Solskjaer struck a killer blow en route to the Treble amid chaotic celebrations at the Theatre of Dreams.
1996: United 2 Sunderland 2
Crowd pleaser Eric Cantona needed to equalise with 10 minutes left after the Rokerites had overturned Nicky Butt's effort. Andy Cole hit a 90th minute winner in the replay on Wearside to keep the side on course for winning the competition.
1994: Oldham 1 United 1 (Wembley)
The clock was ticking down on what would have been a momentous win for Joe Royle's Latics but Mark Hughes conjured up the most sensational of volleys in stoppage time of extra time, from a speculative Butt pass, to break Oldham's hearts and set up the club's first-ever Double.