If you loved South Park: Bigger, Longer & Uncut, try South Park: Post COVID: The Return of COVID
A bridge between a film you've already seen and one most people haven't. South Park: Post COVID: The Return of COVID has roughly 6.3× fewer votes than South Park: Bigger, Longer & Uncut — it's a deeper cut, not a mainstream recommendation. Here's what they share, and what the second one does that the first one doesn't.

South Park: Bigger, Longer & Uncut

South Park: Post COVID: The Return of COVID
What they share
Both films are directed by Trey Parker, and they both carry the playful mood tag, and they sit in Animation / Comedy territory. If that's the register that drew you to South Park: Bigger, Longer & Uncut, the second film will land in a comparable space — through a different lens.
What South Park: Post COVID: The Return of COVID is
A holiday special about time travel and pandemics. Years after Covid destroyed the world, the boys must travel back in time to prevent the virus's initial outbreak. It did give Matt Stone and Trey Parker an excuse to trot out Professor Chaos again.