Tbh as much as I wasn’t a fan of your idea at first, I’m kinda warming up to the HBG being in the stretching room as a professional haterThat’d be cool. I was kind of just envisioning it as the Phantom Manor ghost- skeleton with a top hat and long black coat.
Or like I mentioned earlier, make it the Hatbox Ghost. Hes meant to be one of the “mischievous” ghosts, so it’d kind of make sense we’d see him early in the ride and in the endless corridor before Leota summons the rest of the spirits.