Billie Eilish (and a slight detour onto other IPs)
I covered this topic months ago when she was first speculated, but Billie is by far the biggest IP this year. Not knowing about her is 100% on you, it's hard to avoid her honestly. Admittedly, I am her target age audience so I may be more exposed than most of you on here, but to think that the artist behind the best-performing album of 2019 in the US, and the biggest winner at the 2020 Grammy Awards is somehow a "niche" IP is straight-up lunacy. She has 65 million Instagram followers, anything she posts gets well over 3 million likes - so if we're focused on HHN getting as much publicity as possible, she is definitely the way to go. Beetlejuice could come somewhat close by bringing in both older adult audiences and younger audiences, thanks to TikTok and Broadway, but Hill House IMO won't come as close as you think. Like most Netflix properties, the hype disappears after 1 month of release - that's the big flaw in the Netflix model of releasing all at once... maybe something relevant to the idea of HHN announcing everything at once too.