Benzema follows Charlton because Addicks' defender Kelly Youga is his best mate.
The pair both attended the same junior school together in Bron, France, before they were each snapped up by Lyon's Academy.
Youga told The Sun: "Karim's my best friend in football - he's like a little brother to me.
"We have known each since we were nine years old and we speak often, talking more about Charlton than we do about Real.
"When I moved here he told me it was a good club because they were doing well in the Premier League at the time.
"He told me 'Go there and next year I'll play against you in Champions League'. Sadly it never happened, but he knows all about Charlton and checks on our results."