Friends is, once again, back in the news, as Courtney Cox recently responded to a tweet/Instagram post by Kayne West who claimed that he never found the show funny. West's statement turned out to be more controversial than he may have realized, however, as Friends remains one of the most popular sitcoms of the 1990s/early 2000s.
One of many running gags that showed up from time to time throughout the sitcom was Joey Tribbiani's family, with him as the only son among his seven sisters, who all looked relatively the same. In their first appearance, the episode's entire b-plot centered around Chandler's inability to tell them apart. But each of Joey's sisters needed to be distinguishable in some way or another, whether that be for the plot's purpose at that moment or in order to make a reappearance in a later episode. And while most of the actresses did not move over to the spinoff series, Joey, some did, giving them even more to identify them by.
Mary Therese / Mary Teresa
Mary Therese is one of a few special cases, as she has been portrayed by two separate actresses, Mimi Lieber on Friends and Christina Ricci on Joey. Her name also appears to have a bit of variation, as she is referred to solely as Mary Therese in the original and as Mary Theresa in the latter.
Mary Therese's two appearances bear no resemblance to one another, other than her spoiled and pampered tendencies. Her original character is bold, forward, and direct, but cares very much about the well-being of all of her siblings. Her appearance in the spinoff presents her as very abrasive and uncaring about her family. Physically, she is much shorter in her second appearance, as well as being the second youngest of the family, whereas she was the oldest and tallest of her sisters in Friends.
Mary Angela
Mary Angela, played by Holly Gagnier, is the timidest of her siblings, though, like her sisters, she can be strong-willed. In her first and only appearance of the series, she and Chandler fool around while Chandler is drunk, and he spends the episode attempting to figure out which of the sisters she is.
Even though she is the physically smallest of the group, Mary Angela does resemble her sisters. She is presented to be very comfortable with who she is, despite her shyer nature, and she doesn't hesitate to run to her brother for help when she feels heartbroken by Chandler's actions, exemplifying, for the second time in the episode, that she loves her brother very much.
Dina
Within the events of both series, Joey made many questionable decisions. Threatening to beat up Dina's boyfriend when she reached out to tell him that she was pregnant is a lesser-discussed one, but it's a defining moment when it comes to Joey's over-protectiveness of his little sisters. That said, Dina appears twice throughout the series and has an episode-long character arc, distinguishing her from the rest by quite a bit, and fleshing out her character more so than some of her other sisters.
Dina is the youngest sibling in her family and her defining physical feature in her first appearance is her long hair, but in her second appearance, her hair is cut short. She is played by Lisa Melilli in her introductory episode and by Marla Sokoloff in her second, and she isn't in the spinoff show.
Gina
Of the entire Tribbiani clan, Gina's character is subject to the largest amount of inconsistencies between Friends and Joey. Played by K.J. Steinbern on Friends, she stood at about Joey's height and bore a striking resemblance to the rest of her sisters with a hairstyle to match. In Joey, she is portrayed by Drea de Matteo, and appears as several inches taller, with long, strawberry-blonde hair.
In addition to the inconsistencies in her physical appearance between the two shows, Joey is said to be the oldest of his siblings in Friends, whereas Gina is supposedly Joey's older sister in the show Joey. These changes in her character between the shows, while somewhat confusing, do make her the most easily distinguishable among all of her sisters.
Tina
Tina only has a single appearance out of both of the shows' entire runs, making telling her apart from her sisters much more difficult. She does have some distinguishing features, however.
Tina has a slightly rounder face than most of her sisters and in both of her appearances throughout the episode, wears her hair with a bit of fringe in front of her face. She also appears to be one of the tallest of her sisters. She was played by Lisa Maris and her main character definition is created through a single offhanded comment made once by Joey, where he states that she is no longer allowed to see her husband, who had taken out a restraining order on her. The reason why is left unknown.
Veronica
Like Tina, very little is known about Veronica. The most distinguishing feature of her appearance is her hair, as she appears to wear it in a larger hairstyle than any of her sisters. It is also darker than the others, nearing a blackish color. She has a long face and, like Tina, appears to be taller than most of the others.
Veronica's character is left barely developed. According to a comment in an episode of Joey, she is a big fan of food, like her older brother. She only makes a single appearance between the shows but is, of course, loved just as much by her siblings as the rest.
Cookie
Cookie is probably the most distinguishable of all the Tribbiani sisters. With her slightly deeper voice, short hair, and tough appearance, Cookie is unmistakable among her sisters. Her first introduction to the audience is through a comment on how she once shot her husband, and her final, when she punched Chandler square in the face. It's pretty safe to say, she is seen as the brawn of the family.
Cookie wears a lot of leather and presents as very tough. Despite her only having a single appearance in Friends, she is undoubtedly one of the most memorable Tribbianis in the show.