The 21-year-old joined the Shrimps on a six-month loan earlier in the summer, and has already impressed in his short spell at the Globe Arena so far.
Coming on with the scores at 1-1 just after the hour mark in Morecambe’s EFL Cup first-round clash with Championship outfit Rotherham, Dunn’s introduction kicked off a fiery finale.
Scoring after five minutes on the field with a first-time finish on the edge of the six-yard box, Dunn then saw his goal cancelled out by Jerry Yates, before Rotherham’s Anthony Forde made it 3-2 with less than 10 minutes to play.
But with Richard Wood brought down in the box, Dunn was on hand to score a last-minute penalty kick to level the scores and send the tie into extra time.
Substitute winger Kevin Ellison put Morecambe a goal up, before Dunn put the icing on the cake with a placed finish from the edge of the area.
Yates made it 5-4 with a late consolation goal, but Dunn’s hat-trick had sealed Morecambe progress to the tournament’s second round.
Dunn’s impressive start to life with Morecambe bodes well for his future, with his physical, technique and finishing ability set to trouble League Two defences throughout 2016/17.
The striker is one of eight players currently away from Merseyside on loan, along with Danny Ward (Huddersfield Town), Ryan Fulton (Chesterfield), Adam Bogdan (Wigan Athletic), Jon Flanagan (Burnley, Ryan Kent (Barnsley), Allan Rodrigues (Hertha Berlin) and Lloyd Jones (Swindon Town).