The former flops have blossomed under Louis van Gaal.
Manchester United took back the bragging rights in the city today, as they romped to a 4-2 victory over rivals Manchester City at Old Trafford.
The most incredible thing about the result however, was the players who inspired them.
Young scored the equaliser for United after Sergio Aguero had earlier given Manchester City the lead.
He then went on to set up Fellaini's goal, as well as Chris Smalling's, with sensational deliveries from his right foot.
Fellaini on the other hand was phenomenal. He left Yaya Toure looking like a pup throughout the game, outdoing him for strength, pace and power for the majority of the game - no mean feat.
A year ago, the two were signifying failures in the David Moyes era, and the thought of them bossing a Manchester derby was truly laughable.
But today the result was largely down to their fantastic respective performances.
It did not go unnoticed.
Manchester United fans were quick to make it known how much they appreciated the performances through Twitter...
Fellaini was brilliant, battled Yaya so well and kept him quiet for some part of the game. Link up play with Young was awesome too. #Reborn— Eric Ellie (@EricEllie) April 12, 2015
Fellaini is awesome. Most unplayable player in the league by far when he's in the mood.— Richard Jones (@richjones_1987) April 12, 2015
Young was awesome today. City couldn't handle Fellaini at all— Dis (@BabaMalt) April 12, 2015
@ManUtd Where was Young's nomination? Fellaini was great, but Youngy was awesome!— Victoria (@RabonaNutmeg) April 12, 2015
Young is looking more and more like the player we signed! Such a turnaround, and Fellaini too. The best being brought out of them. #MUFC— Dan'the Gannet'Brown (@DanJBrownMUFC) April 12, 2015
Fellaini and Young! Manchester United Poster Boys of Derby demolition.— JustAnotherRedDevil (@AfridiFan_MUFC) April 12, 2015
#MUFC Booyah! Manchester is all red today! Overpowered City when it mattered. Young & Fellaini are transformed players under LVG.— Ricardo Ascenso (@Ricky_A1) April 12, 2015
Young and Fellaini are doing some incredible stuff on pitch every week.— Achal (@UnitedsRed) April 12, 2015
Not much wins better than a Derby win! Well done, @ManUtd!! Ashley Young and Fellaini played incredible today.— Daniel Rogers (@D_Rogerss) April 12, 2015
What Van Gaal has done to Fellaini & Young is quite incredible. Their transformation has been unbelievable, hats off to them & LVG.— Joe (@JoeTmufc) April 12, 2015