Joan Fontaine established her Toobworld presence in two productions - an episode of 'Mr. Adams And Eve' and in the anthology series 'Climax!' which was about the televersion of Louella Parsons (played by Teresa Wright.)
Olivia de Havilland had plenty of TV credits herself, but none in which she played a fictional version of herself. However, over in the Tooniverse, it's inferred that she exists:
In an episode of 'Rocky & Bullwinkle', Boris and Natasha had suspended Bullwinkle over a snake pit. Luckily Rocky flew in and rescued his friend and they ran off. But Bullwinkle came back,looked down into the hole in the floor and said "So long, Olivia!"
Ms. de Havilland starred in the movie "The Snake Pit".....
"DEATH AND THE DIVAS"
In Toobworld, the rivalry between actress siblings has had a few variations on the Joan & Olivia theme. Chief among them were the rash of murders in the village of Midsomer which centered around Stella Harris and her more successful sister Diana Davenport, a Hollywood superstar. Stella was supposed to get her big Hollywood break with an adaptation of "The Fall Of The House Of Usher", but producer Cy Davenport fell in love with her sister Diana (and married her) and then gave the role to Diana instead. But Stella became the Toobworld version of Hazel Court - the British Scream Queen of the 1960s with the movies "I Thirst For Blood", "Death And The Diva", "The Mummy Rises", and "Torment". Meanwhile, Diana went on to a fabulous career but one in which she lost out on the Oscar for "By Love Divided". ("I was robbed," she told Stella.)
Toobworld Central has another pair who never appeared together in a television episode and never referred to each other in the shows in which they did appear. (But that would be expected if there was a heightened rivalry between them.)
"REQUIEM FOR A FALLING STAR"
The more famous of these two (and the more talented) was Nora Chandler. She starred in a lot of classic Hollywood movies in the forties and fifties, but her star was definitely on the wane by the early 1970s when she murdered her personal assistant. As often happened with Lt. Columbo's murder suspects, it was something she treasured which finally tripped her up. In her case, it was a scene in one of her old movies in which she dressed like a man she had killed and then took his boat out into rough waters to make it look like he died at sea. Unfortunately for her, Columbo happened to catch that scene on the late show.
'THE NAME OF THE GAME'
Magda Blaine was the less talented of the two, but she still made her fair share of movies. (Two of them were "Perilous Voyage" and "Bleeding Heart".) Her main problem was that she was a terrible over-actor and did so even in real life. (Magda was prone to inserting quotes from her old movies into her conversations.) She became an active player in the 1970 military coup which temporarily overthrew the government of President Ben Kaliman in Bhasa. This was not her first time involved in such a venture: two years earlier she was caught up in the machinations of Herman Allison, a multi-millionaire who plotted to bring down the United States government.