Macheda has joined Doncaster Rovers until the end of December and will go straight into Paul Dickov's squad for Friday's home fixture against Yeovil Town.
The Italian has already made five appearances for Doncaster this season in a previous loan spell that saw him score three goals, but a hamstring injury saw him return to Old Trafford.
"I am delighted I have been able to convince 'Kiko' to re-join us as it will add to our attacking options," Dickov told the club's official website.
"I know that he was happy here and knows the set-up well."
McLean has joined Birmingham City on a loan deal that will keep him at the club until January 1.
Birmingham recently lost striker Matt Green to a season-ending knee injury and moved to sign McLean, who has played just six minutes of league football in the current campaign.
McLean scored just twice in 21 Championship appearances last term, although the majority were off the bench.
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