Twice was pretty distinct but I had some difficulty with names. I remember not knowing how to write Jeongyeon's name properly for a month. I listened to some 4minute and liked their stuff a lot but they died just as I got into kpop so I guess it just wasn't meant to be. Red Velvet was the next group. With them, I had a bit of trouble telling Joy and Yeri apart at first. But EXID was the toughest - Hani, Junghwa and Hyelin looked like the same person.
No group has grown on me as much as Twice.