Throwing rocks at trains is an acceptable alternative to engaging in mainstream activities on any given holiday due to your inability to properly participate for any reason. This is taken from Charlie and Mac's tradition in It's Always Sunny In Philadelphia of throwing rocks at trains on Christmas.
I just found out my mom would sell herself to buy x-mas presents for me. Screw xmas, I'm going to go throw rocks at trains.
guy one: It's valentines day and we both are alone.. again. man this sucks.
guy two: yeah I guess we should go throw rocks at trains.. again.
fat girl: Can i come?
guys one and two: Uhhhh... no.