Despite the two having yet to have any screentime together or any in-show confirmation that they've even met, Loona and Octavia have been a decently popular ship for much of the show's run. Mostly owing to both girls having quite a bit in common as two Goth, Jerk with a Heart of GoldTroubled Teen with a complicated relationship with their respective fathers, leading many to think the two girls could easily relate and become fast friends. Though in a variation on this trope, while there are plenty of people who ship Loona and Octavia romantically, there are just as many fan who ship them in a more platonic or familial sense, particularly as the romance between Blitzo and Stolas has only gotten more prominent over the course of the show. The general consensus being that Loona and Octavia would definitely get along great if/when they ever meet.
"Seeing Stars" finally give fans what they wanted to see with Loona and Octavia sharing some screen time together, which is even fairly intimate. While it's unlikely to be intended to be romantic, the episode does show both girls definitely like each other and even get along better than their fathers.
Surprisingly, there is a small but growing fanbase for Moxxie/Verosika Mayday despite the two only having a single interaction in canon; shownbythisart
Stella x Barbie Wire is also a notably popular ship. Not only have these two characters never interacted, even been in the same room together or even know of the other's existence, but one of them (Barbie Wire) didn't appear till season 2. This is seemingly just for the humor and irony of Blitzo and Stolas' sister and wife, respectively, dating eachother, on top of the massive irony of Stella doing the exact thing she shamed her husband for.
Stella x Striker has gained traction with numerous fanart depicting them as more than just employer and hitman and as the counterpart to Stolas x Blitzo.
Verosika/Wally quickly became the new fan favorite OTP of the fandom, after "OZZIE'S" featured the two of them on screen together for a few seconds. Despite the two not having a conversation, and the succubi rudely shoving Wally away when he offered her a drink, the pair became incredibly popular, with dedicated supporters, fan art, andplentyoffanfics.
Striker/Chaz is beginning to pick up steam, even though it is highly unlikely that the duo will ever meet, due to Chaz being Killed Off for Real.
Verosika and Barbie Wire. In "Spring Broken", Verosika potentially implies that they were in the same rehab for at least some time. They also both hate Blitzø, and Verosika is implied to be genuinely attracted to him at some point- so her hooking up with his literal twin sister, who's incredibly similar to Blitzø in both looks and personality just seems fitting. The two have never interacted in canon (at least on-screen, if we'd assume that they've met in rehab).
When the "Unhappy Campers" episode was teased, there was quite a lot of fanart of Barbie Wire hitting on Millie, since a lot of people speculated that this episode will introduce Barbie (and they were right), and she's very commonly headcanoned as a lesbian, so her seeing through Millie's disguise and seeing her as a tomboy/butch woman would be attractive to her. When the actual episode came out, the two never got to interact directly.
by