City have taken charge of their knockout tie against Copenhagen in the Champions League with a 3-1 victory in Denmark.
Kevin De Bruyne put City ahead and trying to defend the strike was McKenna, a surprise signing in January on loan from Forest.
And fans were left baffled when his name was read out as the transfer went under the radar for many.
One fan wrote on X: "Scott McKenna in the Champions League. It's what football's all about, isn't it?"
And another posted: "Can't wrap my head around Scott McKenna playing in the champions league against man city."
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While this fan wrote: "Scott McKenna starting for Copenhagen vs Man City when he couldn't even make the Forest bench most of the time sums up football, unpredictable!"
McKenna was a surprise arrival at Copenhagen this month, joining on loan until the end of the season on January 30.
The Scotland international had been largely sidelined at Forest, where he had made just five appearances in the Premier League.
After the arrival of Nuno Espirito Santo as manager, McKenna's chances in the first team dropped even further.
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The decision was made to loan out the 27-year-old, leading to a move to Copenhagen where he has since made his Champions League debut.
Whether he leaves Forest for good in the summer remains to be seen as the club look to offload bit-part players to adhere to FFP rules.
City might have taken the lead against Copenhagen but they were pegged back later in the first half after a horror mistake from Ederson.
The ball eventually found its way to Magnus Mattsson's feet, who delivered a sweet strike to grab the equaliser and send the Parken crowd crazy.
However, the European champions went up another gear and retook the lead through Bernardo Silva's finish before Phil Foden added another deep into stoppage time at the end of the game.