Complex sentence: At the theater, Maggie sees a "Flyday the 13th" film poster with a fly wearing a hocky mask and wielding a machete, a reference to the Friday the 13th film series.
Split into simpler sentences: At the theater, Maggie sees a "Flyday the 13th" film poster with a fly wearing a hocky mask and wielding a machete. This is a reference to the Friday the 13th film series.