don't know if it counts, but shortly after the juggernaut update
I wanted to try my new yasuo mystery skin (project yasuo) and so I tried playing Twisted Treeline. I got matched against an arcade riven, a final boss veigar and an arcade hecarim (jungle). I had a skarner and a Gnar (gnar went jungle, which was both strange and awful- awful in that he got executed several times trying to clear and hecarim abused that fact to invade him several times). Fortunately both of my teammates when tank when they realised they were behind and we actually ended up pulling a victory after I managed to tilt their veigar with a very well-timed windwall to save skarner's life.
I had to lane against the riven, both of us were just trying out a skin- which was reflected in our gameplay where both of us were zoned off the minion wave and playing extremely passive/cautiously because neither of us wanted to trade (because we both assumed the other was actually good at the game).
At the end of the game, I asked them if they were a group, and it turns out all 3 players were randoms who just so happened to pick the arcade line of skins.
The closest on summoner's rift, was all 4 champions picking the skt t1 set- except for their zed mid who went shockblade.