The Slayers Parody refers to two parodies seen in the anime Slayers.
The first one appears in episode 17 of the first season.In this episode, the characters Lina, Amelia and Gourry are running away. In order to do it, they disguise, and Gourry has to use a sort of Sailor Moon costume.
The second one is in episode 14  of Slayers NEXT. In this episode, Lina and Amelia have costumes similar to Sailor Mercury and Sailor Chibi Moon, while they sing the song Otome No Inori.