There is few groups that I thought already debuting in second or third generation just because I think I have heard about them before and turn out they are just debuted around that time I know them. My mind love to play tricks with me.
Here my list:
•GFriend - I just thought they're from second gen when I discovered them in 2016.
•Everglow - I thought they're from from third gen.
•Weeekly, Purple Kiss and Saturday -They just remind me of AoA. I don't know why but it just ring the bell for me. As soon as I heard their name, I just thought oh, they're probably from the 2nd gen.
•Oneus, P1Harmony - Third gen and without any reason. My mind just give me false flashback about them.
•Cix, E'last, N.Flying - I thought they're from second gen because of their name, which still I don't know why their name scream 2nd gen for me at the first, huhu.
•T1419 -Still didn't know how to pronounce their name and I expect they are from first gen because of 1TYM. Their name sounds really first gen for me because of this.