Rick and Morty season 5 has revealed new details about Rick’s relationship and history with Birdperson in “Rickternal Friendshine of the Spotless Mort.” In the past, Rick has called Birdperson his best friend, and it’s been known that the two fought together in resistance against the Galactic Federation, but specifics from that part of their lives have been harder to come by. In Rick and Morty season 5, however, much of the duo’s early days is explicitly shown, possibly hinting at a relationship that was more than platonic.
In Rick and Morty season 5, it’s revealed that Rick first met Birdperson at a music festival in space, where they got high and formed a band with Squanchy. After realizing that their antigovernmental values aligned, the two worked together closely as part of the resistance against the Federation. Though that entire group was clearly tight-knit, Rick and Birdperson were particularly close – that is, until Rick’s trans-dimensional nihilism superseded his political convictions, leading to a schism between him and Birdperson that would never fully heal.
Throughout Rick and Morty, there have been hints that Rick might have seen Birdperson as more than just a friend. At Birdperson’s wedding, for instance, Rick is disgruntled and prickly from the beginning. That could be simply because he disagrees with the idea of marriage, or it could be a glimmer of jealousy. In season 4, there’s a non-canon scene that shows Rick and Birdperson dancing and singing as if in a Broadway musical, with a few moments looking particularly intimate. Still, none of that proves anything beyond friendship.
Then, in “Rickternal Sunshine of the Spotless Mort,” Rick and Morty shows the Battle of Blood Ridge, where the split between Rick and Birdperson took place. Rick asks Birdperson to come away with him to travel the infinite cosmos, but Birdperson declines, stating that his relationship with Rick isn’t worth giving up his moral and political ideals. Rick immediately blanches at the use of the word “relationship,” shooting some quick insults at Birdperson before vanishing through a portal. Later in the episode, in reference to Tammy, Birdperson says that people don’t get to choose who they love, to which Rick responds, “You got that right, why do you think I’m still f***ing down here?”
Again, all of this could be read in a strictly platonic way, and since Rick doesn’t have that many real friendships to begin with, that’s a perfectly plausible interpretation. But the Blood Ridge scene specifically hints at something more. Rick’s vulnerability and immediate turn on Birdperson is written strikingly like a breakup scene, with Rick revealing how important Birdperson is to him, and Birdperson confessing that his work is more important to him than Rick. It's also worth noting that the Rick and Morty comics feature a glimpse at an alternate reality where the two characters are romantically involved. Given Rick’s apparent pansexuality, documented on many planets across the multiverse, and given how close he and Birdperson became, it would make a lot of sense for him to have developed stronger feelings for his friend. Now that Birdperson is alive again, it might be possible for the two to mend the gap between them. But after Rick withheld information about Birdperson’s daughter from him for personal reasons, it might be a while before Rick and Morty sees the two reunite again.