Isabella Rossellini appeared as herself in "The One With Frank Jr." when she walks into Central Perk for coffee. Earlier on in the episode, Ross had made a list of celebrities he was allowed to sleep with and cut Isabella out of the final laminated draft.
As Ross proceeds to hit on her, his friends watch on. She is bemused by his daft comments throughout this conversation, particularly when he mentions having a list of celebrities he'd like to sleep with and then making it pretty obvious that she is not on it, causing her to publicly humiliate him.
Isabella was born in Rome, Italy (June 18th, 1952) and holds joint Italian-American citizenship. She is an actress, filmmaker, author, philanthropist and model. Among her notable film appearances are Blue Velvet and Crime of the Century for which she received a Golden Globe Award nomination. Married to film producer Martin Scorsese from 1979 to 1982, she was also the partner (1994-96) of Gary Oldman who appears later in the series as Joey's co-star in the WW1 film he shoots in "The One With Monica And Chandler's Wedding, Part 1".