I'm a bit fuzzy on dbz time-line but godsss the idea of kid piccolo meeting 18 and 17 when they were still fully human...... And they were already weirdos so they decided to befriend this weird green kid....... (I've said it before but Piccolo's appearance shouldn't actually raise any flags. The mayor is a dog person!)..... And Piccolo leaving them after a year to get his revenge in Goku and they wish him luck and tell him to visit after he's done.... And he does he does he does! He comes back after healing from his fight and having a mild existential crisis but they're not here. Their house is deserted. There are signs of struggle. Blood. He can't feel their energy anywhere (already too changed by the experiments) which means they're dead. One more reason to hate people.
And then years after..... Piccolo having no idea who 18 and 17 are because obviously those weren't their names when he knew them. And when he sees them there's a moment of complete shock and then full denial because they don't feel anything like his first friends. In fact they don't feel like anything at all. When he only sees one of them he thinks it's a really weird coincidence but seeing the second one rules it out. And then he just keeps trying to tell himself that those aren't his friends, only robots wearing their skin. But 17 wears the same kind of clothes. 18 closes only one eye when she laughs. They have the same smiles. They both stick their tongues out at each other when bickering. He can't even tell himself his old friends wouldn't have done such horrible things because even when they were human they were honestly pretty okay with murder and it must have gotten exacerbated.
From then on it's a lot of anger (for what was done to them), grief (for what was done to them) and dread (for what he'll have to do to them, to save humanity).
He would have some hope of changing their minds like he changed his but Piccolo and Gohan had several months that Piccolo, 17 and 18 don't have. And also they don't remember anything from before. In addition, Piccolo's pretty sure that if that were going to work, his future self would've done it.
It's a mess.
Too much of a mess for anyone to notice that he switches from "killing the androids" to "saving the androids" a little too easily. Too much of a mess to notice the way his antennas droop when said androids get absorbed by Cell. Too much of a mess to notice that suddenly Piccolo's grudge against Cell is a lot more personal. It's personal for everybody isn't it? The future of their planet is at stake. Nothing weird in that.
(Gohan notices)
Piccolo's the one who asks Shenron to get the bombs off them this time. Just the idea of his newly returned friends suddenly exploding one day fills him with dread. Sure they don't remember him, but these last few years he's been trying out this kindness stuff.
(this wish gets him the androids' attention)
17 and 18 end up pestering Piccolo from time to time. He's fun to tease and strangely more at ease with them than pretty much anybody else who knows they destroyed the world in an alternate future.
(he tells them it's because he probably destroyed the world in another alternate future, too. Partly true. But, of course, only partly)
(there is a minor crisis about 17 and 18 being so very different from the people he knew in what little childhood he had. Yes they look the same and act pretty similar but he perceives things as much with his mind than with his other senses and telepathically speaking they're nothing like what they were before)
(the crisis is resolved when he figures out that he can just try to become friends with the people they are now)
And maybe 18 and 17 remember when they were human and they met a little green kid who rapidly became a green teenager who became a friend. Maybe they don't. But they stay friends, nonetheless.
