Shanghai - Amid some oohing, aahing and tumbling, a child star was born on Sunday.

Actress Cecilia Cheung and comedian Stephen Chow announced that her three-year-old son, Lucas - one of the most photographed tykes in Hong Kong - will record a duet with her for Chow's animated film, CJ7 2.

It will be an entertainment debut for the son of actor Nicholas Tse and grandson of erstwhile matinee idol Patrick Tse.

The press conference was interrupted by Lucas himself, who scrambled on stage as Chow, a one-time children's television host, said: 'You came out before we announced you.'

Speaking into the microphone of his mother, who gave birth to his brother, Quintus, last month, Lucas told the media in English: 'I love you... Don't say my mother's fat.'

But as their cameras clicked non-stop, he told them: 'You're naughty.'

Darting and crawling around as the adults spoke, he got the media in a tizzy and at one point, fell to the floor with a plop. He refused to be helped back to his seat by Chow, said Sing Tao Daily.

Cheung made her debut in Chow's 1999 film, The King Of Comedy. She said she picked CJ7 2, the sequel to his 2008 film on a cuddly alien creature, for her first post-maternity project and her son's debut to show her gratitude.

Chow said the collaboration came up during a chat, when Cheung told him Lucas did not speak much Mandarin. 'Since Lucas likes CJ7, I proposed that mother and son sing the theme song and Lucas could learn Mandarin on the side.'

Cheung said: 'Actually, my plan was to have him concentrate on his studies. I never thought about him being in show business.'

Because 'the Hong Kong media make him a cover boy every week and wait for him outside the kindergarten every day', she thought she would play along and let him have fun during the making of CJ7 2.

Asked what her husband thought of her decision, she demurred. 'I'm just a little woman. You should ask my husband yourself.'

This article was first published in The Straits Times.