Two gay men driving around trying to pretend they are straight by attempting to yell at girls through the window. But rather than actually yelling something useful to pick them up, they yell something ridiculous like "DOHHHH!" and then boyishly giggle about it in the car. Then they go home and have gay sex and grand pappy smash each other.
Dialogue of a Filly Run:
Bobby: Hey Dan... look there's a girl.
Danny: Cool man.
Bobby: Wanna try to talk to her?
Bobby & Danny: (out the window to the female) DOOOOHHHHH!
Danny: Let's go have gay sex.
Bobby: Yeah, definitely. And grand pappy smash each other too!
Bobby & Danny: OH YEAH!