This just occurred to me that I should ask and I'm sorry if I've messed up.

I was hoping to use Hemlock's father in a thread with Ruffnut as an NPC, who would I need to co-ordinate that with? I'm not sure who wrote his video response to Ruffnut.

I wouldn't need them to completely NPC the character since I know everyone's busy, I just thought I should touch base with them before I move ahead with my plans.