Jennifer Aniston and David Schwimmer were apparently crushing hard on each other during the earlier seasons of Friends, although nothing came out of it. The actors played on and off couple Rachel and Ross for 10 years until the show ended in 2004 where they ultimately reconciled and ended up with each other. Like their characters, the pair were into each other, but they didn't end up acting on their feelings.
To say that Ross and Rachel's romance in Friends was tumultuous would be an understatement. Despite having mutual feelings for each other, becoming a couple was actually very difficult. For years, Ross was pining for his sister's friend but he never had the courage to actually confess his feelings. By the time they reconnected after a while, he was given a chance to finally make his move but a series of events that included both of them being in separate relationships hindered their eventual coupling. But, Friends gave in to the story, and by season 2 they eventually became a couple.
Aniston and Schwimmer effectively played the will-they-or-won't-they dynamic for Ross and Rachel. A big part of it is because the actors have great chemistry with each other, but aside from that, there might not even be that much acting involved. During the Friends reunion on HBO Max, officially titled Friends: The One Where They Got Back Together, host James Corden brought up the subject of off-screen romances, which led to Aniston itting that she did have feelings for her on-screen love interest and that it was reciprocated. Schwimmer, on his end, expounded on the revelation and explained that there was a time that the attraction between them became really intense. Unfortunately, the timing just wasn't always right because one of them was always in a relationship when the other wasn't and they just "never crossed that boundary."
Later as the HBO Max project tackled Ross and Rachel's relationship, Schwimmer continued to reminisce on the first year or two of the sitcom and revealed that he and Aniston would cuddle on the couch at Monica's apartment during filming breaks. The Friends reunion shared behind-the-scenes footage of the pair corroborating his story where they're being very flirty and playful with each other. Schwimmer then shared that at that point, he was wondering how the others didn't know they were "crushing on each other," to which their cast mates countered saying that they "knew for sure." Despite their missed connection, their co-star Courteney Cox did raise a great point: it would've been difficult for Aniston and Schwimmer to continue working on Friends if they pushed forward with a romantic relationship if it ended up failing.
Reel-to-real life romances are not unusual as many stars in Hollywood meet each other through work and then fall in love. Given the on-screen situation that Ross and Rachel were in at that time, it wouldn't have been difficult for the Friends stars to develop an attraction to each other. However, since both Schwimmer and Aniston have been so open and candid regarding their on-set flirtations, not to mention both going forward with their respective love lives, it's safe to say that they've gotten over the idea of what could've been long ago.
Friends' Ending Almost Didn't Have Ross & Rachel Get Back Together