A big skid mark

Lucy saw a long brown stain in the seat of Erza's panties and it was giving off a horrible stench. She quickly snaps the panties back and waves her hand in front if her face.

"PU!!" She exclaimed. "What's wrong?" Juvia/Erza asked concerned. "Well the good news is that you didn't crap yourself. The bad news, I don't think you're gonna wear those panties ever again, Erza!" She laughed. Both of them blushed. Knowing very well what she meant.

"So, should I call Virgo to get you some new undies, or a diaper? Cause I think you're gonna need one!" Lucy asked before she broke down laughing.