The EU boss startled chief Brexit negotiator Guy Verhofstadt ahead of a debate on the Future of Europe when he crept up behind him and pretended to give him a haircut.
It was unclear if Mr Verhofstadt saw the funny side of Mr Juncker’s barber chair performance in the chamber of the European Parliament but photographs capturing the moment did not show too many smiles.
Mr Juncker is often seen trying to spread the love with with his trademark kisses, cuddles and hugs.
Some recipients of his ostentatious shows of friendliness often seem less than impressed as he ruffles their hair, massages their shoulders or grabs them in a tight embrace.
Last year bizarre video footage emerged of Brussels’ top bureaucrat repeatedly slapping member states’ leaders in the face, hopping from foot to foot dancing and even kissing one male delegate after marvelling that they were wearing the same colour tie.
And last year Mr Juncker was pictured planting a kiss on the bald head of Commissioner for Economic and Financial Affairs Piere Moscovici before moving on to German Commissioner for the Digital Economy and Society Guenther Oettinger who he greeted with neck-rub.
He has always hit back at critics of his unstatesmanlike behaviour in the often dour surroundings of Europe’s corridors of power, insisting he is “a human being, not a robot”.
But in 2016 he was forced to deny having a drink problem when rumours that circulated around Brussels for many years came to the surface with one senior diplomatic source claiming he “has cognac for breakfast”.
During the interview with French newspaper Liberation he defended his record as he consumed numerous classes of champagne.