We delved into the archive to find out. Follow every key moment of tonight’s cup tie on our live blog, at www.thestar.co.uk.
1. Oliver Norwood of Sheffield Utd celebrates scoring the second goal during the FA Cup match at The Den, London. Picture date: 25th January 2020. Picture credit should read: Robin Parker/Sportimage
Ollie Norwood scored at The Den to seal United's fifth-round spot - what happened the last five times United reached that point? Pic: Robin Parker/Sportimage Photo: Robin Parker
2. Gunner-ed down
In 2004/05, United earned a replay against Arsenal but lost a penalty shoot-out at Bramall Lane Photo: Steve Ellis
3. Phil Jagielka and Paddy Kenny salute Blades fans after the game
Kenny had an injection before the game to help him get through it - but it meant he could only dive one way in the shoot-out! Photo: Dean Atkins
4. More heartbreak for Kenny
In 2008, United's fifth-round tie again went to a replay against Middlesbrough Photo: PAUL ELLIS