The 'Girls Just Wanna Have Fun' singer, famed for high-pitched voice, was spotted sucking the voice-distorting gas out of balloons back stage at the Hetrick-Martin Institute benefit gala, in New York, last week.
A source told the New York Daily News newspaper: "Cyndi sucked the gas out of two helium balloons before going on stage to belt out 'Time After Time' and some of her other hits."
The 54-year-old singer also managed to upset her teenage backing singers at the charity concert - which raised money for the Harvey Milk High School for Lesbian, Gay, Bisexual and Transgender (LGBT) youths - when she introduced them to the audience as her "transgender choir".
One of the young singers fumed: "She keeps calling us transgender! We're not f***ing trannies!"
The Scissor Sisters also performed at the Institute's gala dinner.
TAGS: Music Cyndi Lauper