'Immaturity For Charity' has a better-known cast than some Irish movies, but all the actors who took part gave their services for free in aid of St Francis's Hospice, Raheny.
One standout sketch features Domhnall as a grown man waking up in bed to his parents, played by dad Brendan and mum, actress Cathy Belton, giving him the facts of life.
"Being 28, the son tells his parents he already knows about sex, yet they persist – but what makes it funny is their unusual view on the subject," Domhnall told the Irish Independent.
"Dad giving me the sex talk was hilariously awful and hilariously funny at the same time," he said.
"Rehearsing with him made me laugh more than anything else I have ever done."
Coincidentally, when his father picked up a Rising Star Award on behalf of his absent son Domhnall at the IFTAs last year, he joked he could never get his son out of bed as a boy.
The comedy has already raised €20,000, but producers hope to raise more, with Domhnall appealing for more funds during the broadcast.
Tipped by 'Variety' magazine as one to watch in 2012, things look even better for the Malahide man in 2013 when he stars in his first lead role, a comedy, 'About Time', from 'Four Weddings And A Funeral' writer Richard Curtis.
Donations to the project can be made via www.immaturityforcharity.com.