to rain on someone's parade, to diss their set. Reference to cakefarts.com. To disrespect someone so much that you walk into their birthday party, and proceed to deficate on their cake.
Fartin' around the turd is a figure of speech used to imply that somebody or something is wasting time or procrastinating.
This figure of speech comes from the actions of a gaseous individual, who instead of going to the bathroom and dropping a deuce, with just sit there and fart around the turd all afternoon.
"Hey Justin, quit fartin' around the turd, these are open-air cubicles and it's starting to smell like raw sewage in here."
"Hey Joe, quit fartin around the turd and do your taxesalready."