During the ending to the '2017 SBS Gayo Daejeon' back on December 25, a Black Pink fan's fancam spotted the girls greeting TWICE, and showing their friendship with Red Velvet. Rose was spotted talking to Irene and Yeri and giving Yeri a hug, but more notably, Lisa stood back to hang out with the Red Velvet members - especially Irene.
She looked excited to see Irene and bowed excitedly twice to greet her. They held hands and talked as they walked down the stage, and Lisa was so engrossed in interacting with Irene that she almost missed her group photo with the rest of Black Pink.
You can check out the moment below at 2:43. Did you know they were friends?