Avril celebrated Halloween early this weekend as she attended, not one, but two Hollywood events in celebration of the spooky holiday! First up, she attended a party hosted by fellow popstar Halsey, dressed as '80s pop icon Madonna. The two even performed an impromptu rendition of Avril's 2007 hit "Girlfriend"! Guests also made donations to the charity My Friend's Place. The next evening, Avril went in for round two as she attended the UNICEF annual masquerade ball, dressed in a stunning silver dress, glittery silvery boots, and blue hair. See more photos of Avril's night out on the town below!