E.Na – background vocals (on "What Is Love?" and "Stuck") Park Soo-min – background vocals (on "What Is Love?", "Sweet Talker" and "Ho!")
E.Na – giọng nền (cho ca khúc "What Is Love?" và "Stuck") Park Soo-min – giọng nền (cho ca khúc "What Is Love?", "Sweet Talker" và "Ho!")