A DJ killed a man after waking up at a party to find a penis had been drawn on his face, the Old Bailey heard.
Vanessa Barrows, who had hosted the ten-hour party at her flat in Tooting, south London, told the court everyone at the party was enjoying themselves.
But the joke turned sour when the 'boy banter' got out of hand and party-goer Anthony Thompson, 26, was punched to the ground outside.
Mr Thompson's head struck the floor and he died from brain damage, jurors heard.
Thomas Evans, 32, from Morden, Surrey, denies manslaughter following the all-night party in February last year, claiming self-defence.
Anthony Thompson (left) was killed with a single punch by Thomas Evans (right). Evans says he was acting in self defence
Mr Thompson's head struck the floor after the party and he died from brain damage, jurors heard
Vanessa Barrows drew the penis on Mr Thompson's head in lipstick at her flat in Tooting, south London
She said Mr Evans had fallen asleep in an armchair when morning approached and some condoms had fallen out of his pocket.
She added: 'I got my lipstick out and drew a penis on his face. It was done for a laugh.'
Miss Barrows said that when Evans woke up, he had seen the funny side of it.
She also nodded off and woke to find a row going on. She said: 'It was just silly boy banter between Anthony and Tom.
'Anthony was saying about who was stronger than who. It was a joke. They were friends.'
Miss Barrows said Mr Thompson had been trying to wind Evans up, while Evans was not reacting and was trying to calm things down.
After people started to leave, she heard scuffling outside and found Mr Thompson on the ground when she got downstairs.
Peter Clement, prosecuting, said that when Evans woke up he seemed to take the drawing on his face in 'good spirits'.
As the banter continued, Mr Thompson was heard to say in bravado: 'I can knock any one of you blokes out.'
Evans replied: 'You couldn't knock me out.'
Mr Clement added: 'That set off a chain of events.'The trial continues.