@HumanoSiniestro
They only pick something widespread. Like politics, celebs, big stories of the day. Besides brony culture has been on a decline ever since 2013.

In south park the stick of truth when you visit a secret girls club to make yourself look like a girl so you can make an abortion while a huge zombie nazi fetus is fighting against a us army (pretty dumb). In that girls club there is a pony poster called my little horse with irl horse on it. can be considered a reference.

@Soft Lava
Hey, you're right. I wonder why they haven't made an episode making fun about us.

Here's two boring facts

Fact number one: South park creators made fun of everybody so far. Except for bronies.
Fact number two: One of mlp episodes shows south park's clothes as an easter egg. Pretty dumb.