Typically streaming services keep all of their viewer data secret. Netflix doesn't even tell producers how their shows are doing. But Hulu just bucked the trend and got a little transparent about the most popular show it carries.

The secret knowledge now made public is this: People are still watching a lot of South Park.

According to The Hollywood Reporter, Hulu CMO Kelly Campbell disclosed during the streaming platform's upfront presentation to advertisers that the long-running Comedy Central animated series is the most-watched show on Hulu. Subscribers cumulatively watched 135 million hours of South Park in 2017, she said.

Hulu had 17 million subscribers at the end of 2017 (it's up to 20 million now; Hulu is thriving), which means that Hulu subscribers watched 7.94 hours of South Park per capita in 2017.

On the surface, it may seem surprising that South Park is the most popular show on Hulu, but it tracks. Anecdotally, people use streaming TV as comfort food, and for a lot of people between the ages of, say, 25-40, South Park was a formative show and watching library episodes now is like hanging out with old friends — you could say it tastes like member berries. Its good-enough new episodes keep subscribers coming back and then revisiting old episodes. Plus, it's been on for 21 seasons and has almost 300 episodes, which allows fans to binge it in bulk. It's also been available to stream exclusively on Hulu for years, so people know where to find it, which is no small thing.

The 20 Greatest South Park Episodes of All Time

It just proves that Hulu knows what it's doing by buying huge libraries of old shows. That's what people want to watch.

South Park is returning for Season 22 on Comedy Central later this year. In the meantime, of course, (almost) all episodes are available to stream on Hulu.