There were a few videos showing real-life Grass popping a boner while interacting with Sweek...

(Albeit creatively edited. He already had one before meeting Sweek in the paddocks.)

Magical Lesbian Spawn

Seen plenty for both ponies and 2hus.
Eh, it's normal when there's almost female casts.

And that is how Daring Tact's granddam (Cesario) was born /s