Michael Douglas has revealed he is planning his father Kirk Douglas's impending 100th birthday, but admitted it is becoming a bigger event than he had expected.
The younger Douglas also said his Hollywood star father is "doing great" as he approaches the landmark age, and he can see him "going on" to live longer.
Appearing on ITV's The Jonathan Ross Show, the 72-year-old actor said: "He is 100 on December 9 and I'm in charge of planning the party.
"He's doing great, he's doing absolutely great, he's got a walker with wheels. He tends to fly, he's at about a 45-degree angle at all times and moving great."
He added: "I said, 'let's maybe have an afternoon lunch', but then he doesn't like to watch people eat so we said, 'let's do a tea', so we're down to a tea and we're just trying to get the details worked out, but it's turning out to be a major function."
Asked what he could give his father as a present, he said: "I'll probably wish him 101. He is rocking, I can easily see him going on."
The Wall Street star revealed that his Academy Award-winning father is still working, and is writing his 11th book with his wife Anne.
He said: "They've been married and she's been my stepmother for 65 years. I've noticed they're working on a book together so he's quite content, quite satisfied, he's just an extraordinary guy.
"It's a real incredible rags to riches story: Russian immigrants came in 1914, he was born 1916 when he was here, his parents never really learned to read or write English, it's a wonderful immigrant story."
He spoke fondly of his multi-talented father's past as he added: "He went to college in the back of a manure truck, he was a wrestling champion and then just graduated from there, became a tremendous success, then about 15 years ago, he proceeded to give away all this money he has made, so he's been very charitable and returned everything back.
"I'm super, super proud of him."
During his stint on the TV chat show's sofa, where he was joined by British stars Michelle Keegan, John Bishop and Keith Lemon, he also spoke about his long career in the movie industry and how his father had a great influence on him.
He said: "I have been very fortunate that was a great, great time of my film-making. (The) 70s and the 80s was a wonderful time ... an independent time when the studio boss was the boss, before all this vertical integration of the entertainment business has happened.
"And it's also the biggest benefit of being second generation, growing up with my dad and seeing all the foibles and insecurities of movie stars and how they conduct their lives."
The Jonathan Ross Show airs on Saturday at 9.50pm on ITV.