Clone swaps are done when original Pokémon are cloned using one of the various methods (two system glitches, Power Saves, etc.) and the clones are then swapped so that both users each have both Pokémon.
Where there is only one person able to clone, there is a bit of a trust factor; however, it sounds like you were going to trade two of the Pokémon away anyway, so I was offering to swap clones so that you can get a Shiny or two yourself that you don't have (I can go through my Bank) - and same with me - and then I can clone it/them the same as the one(s) I send you and send them right back a few minutes later.
Off the top of my head, random catches I had that are Shiny include several Teddiursa, some Audino, a couple of Chansey, and a horde Bellsprout (THAT was a pain to nab). I also have numerous others in trades including a Clawitzer, a Barboach, and many others; I'd have to scan as it's too many to remember. :)
Where there is only one person able to clone, there is a bit of a trust factor; however, it sounds like you were going to trade two of the Pokémon away anyway, so I was offering to swap clones so that you can get a Shiny or two yourself that you don't have (I can go through my Bank) - and same with me - and then I can clone it/them the same as the one(s) I send you and send them right back a few minutes later.
Off the top of my head, random catches I had that are Shiny include several Teddiursa, some Audino, a couple of Chansey, and a horde Bellsprout (THAT was a pain to nab). I also have numerous others in trades including a Clawitzer, a Barboach, and many others; I'd have to scan as it's too many to remember. :)