The supermodel and the 'Piranha 3D' actress agreed to play sworn enemies Alexis and Krystle in the £1million reboot of the iconic 80s TV series - which was unveiled at the Topshop boss' 60th birthday party in Mexico.
A source told The Sun newspaper: ''Philip is a hard man to please - after all, what do you get the man who has everything?
''But he's a huge 'Dynasty' fan and his wife thought it would be great fun to have him and his family starring in a spoof episode.
''Kate and Kelly added some glamour as Alexis and Krystle and everyone loved it.''
Meanwhile, 38-year-old Kate has also been flexing her acting muscles with a cameo in UK comedy show 'Absolutely Fabulous' - where creator Jennifer Saunders praised her complete lack of diva behaviour.
She said: ''Kate's great, she's lovely. She behaved so nicely and was such a sweet person. She didn't have any tantrums or any airs or graces. There was no nonsense.''