The former Dynasty actress joined the cast for the finale of the sixth series, which was aired on Thursday evening at 9pm, playing glamorous Chairman and CEO of the Solana Hotel Group, Crystal Henessy-Vass.
Dazzling in a black and white dress with white jacket and a decorative brooch, Joan, 80, holds a cigarette in her hand as she arrives to inspect the 4-star Benidorm hotel.
She soon creates havoc as she demands that the hotel receptionists call the hotel manager Joyce Temple Savage, played by Loose Women star Sherrie Hewson.
"Now listen to me," says the no-nonsense boss. "I am going to take a seat over there and you, young man, are going to bring me a large gin, slimline tonic and an ashtray."
When asked who is waiting, Joan names her title, "in other words, top dog kiddo, top dog."
The five-times-married actress, famous for her role as Alexis Carrington Colby in the 80s American series Dynasty – for which she won a Golden Globe for Best Actress in 1982 – tweeted her excitement at the role last year.
"Looking forward to going to Spain to be in #Benidorm, And I'm playing Crystal' yes I am !! But not the dynasty one," wrote the English actress.
She reminded fans to tune in to the show on Wednesday. "Don't forget to watch @benidormonline I'm on the show tomorrow night as Crystal !! Yes I am," she wrote.
Paddington-born Joan made her stage debut at age nine and went on to train as an actress at famous acting school RADA, before appearing in several British films.
She headed Stateside to Hollywood at 22 where she was successful in landing a series of roles in popular films including The Girl in the Red Velvet Swing and Rally 'Round the Flag, Boys!. She landed her role in Dynasty in 1981.