Cool bit of half-rumor half-basically-confirmed trivia.
Back in the early days of vtubing there was a group called Gamebu, mostly know these days for an infamous scandal where they mistreated and then replaced the talents behind their members and basically killed their audience because of it.
Anyway, Gamebu had a skit team. They would do short, scripted videos, using 3d animation, stock assets and backgrounds, and
quickly developed a rapid-fire,
absurdist style. Videos were around 1 minute at most. They even tagged their videos titles "【アニメ】".
In April 2019, Gamebu's talents quit due to some sort of mistreatment, but were able to negotiate a return later that month. Likely because of this, in June, Gamebu started replacing their talents. The last Gamebu skit in what we now know as the Hologra style was released on June 10. After that, Gamebu's skits transformed into 5-10 minute short story style videos with a completely different writing style.
Hologra started in May 2019. The overlap can probably be explained by episodes already in production. Of course it was never officially said that this was the old Gamebu team, but I think the style overlap shows it 99%. And to this day I think picking up the Gamebu skit team is one of Cover's biggest wins.