It is all the more remarkable given that Ronaldo left Manchester 12 years ago and Ferguson left eight years ago.
“It's like a dream come true, after all the times that I went back to play against Manchester United, and even as an opponent, to have always felt such love and respect from the supporters in the stands... I'm back where I belong!” the Portugal star wrote.
Many will contrast this emotional homecoming with the departure of Lionel Messi, a player with skill on a par with Ronaldo, from his long-time club Barcelona to the big-spending Paris Saint-Germain.
Is Ferguson the greatest manager in Scottish or even world footballing history?
Competition for the Scottish title is fierce with the likes of Jock Stein, Bill Shankly and Matt Busby. But even some of the less celebrated names have some high-profile fans with Leicester and Denmark keeper Kasper Schmeichel praising former Falkirk boss John Hughes for playing a key role in his development during a spell with the Bairns.
On the global stage, Pep Guardiola is lauded by many, but his successes came at big clubs, while Ferguson took what was a relatively small provincial club in European terms, Aberdeen, to glory in 1983 with victory over Real Madrid in the European Cup Winners’ Cup final. Perhaps Guardiola should consider attempting a similar feat.