VAR sealed a brace for Leicester striker Kelechi Iheanacho, while Jon Dadi Bodvarsson worked through the Reading wardrobe for a hat-trick.
Former Manchester City striker Iheanacho opened the scoring with an assured finish three minutes before half-time against Leicester’s League One opponents and thought he had been denied by the offside flag inside the final quarter of an hour.
However, the video assistant referee system showed the 21-year-old was onside when played in by Riyad Mahrez, the goal stood and a trip to Peterborough United in the next round was secured.
The Football Association is trialling the technology during this season’s competition and Iheanacho stands as its first ever goalscoring beneficiary in English football.
Premier League leaders Manchester City must travel to Cardiff City in round four after a Junior Hoilett brace helped them to a 4-1 win over Mansfield Town, the League Two club having been level at the interval thanks to a Danny Rose goal.
West Ham needed extra-time to see off Shrewsbury Town 1-0, with Reece Burke’s maiden senior goal decisive in the 112th minute as England goalkeeper Joe Hart captained against the club where his career began.
Jon Dadi Bodvarsson claimed the matchball as Reading beat Stevenage 3-0 and will have two match shirts with which to commemorate the occasion.
The officials decided Reading’s blue and white hoops clashed with their visitors’ white and red tops and blue shorts too much for comfort, meaning the hosts and their hat-trick hero re-emerged in orange shirts for the second period.
There were no such fashion faux pas as Marco Matias and Atdhe Nuhiu saw Sheffield Wednesday past Carlisle United in a 2-0 victory, earning a home tie against Reading, who will no doubt pack their away kit.