Singer Katy Perry (R) poses with UNICEF Executive Director Anthony Lake after she was appointed UNICEF Goodwill Ambassador at the UNICEF headquarters in New York, US, on Dec. 3, 2013. Katy Perry will focus on improving the lives of the world's most vulnerable children and adolescents, according to the UNICEF. (Xinhua/Niu Xiaolei)

Singer Katy Perry attends a panel discussion before being appointed UNICEF Goodwill Ambassador at the UNICEF headquarters in New York, US, on Dec. 3, 2013. Katy Perry will focus on improving the lives of the world's most vulnerable children and adolescents, according to the UNICEF. (Xinhua/Niu Xiaolei)

Singer Katy Perry attends a panel discussion before being appointed UNICEF Goodwill Ambassador at the UNICEF headquarters in New York, US, on Dec. 3, 2013. Katy Perry will focus on improving the lives of the world's most vulnerable children and adolescents, according to the UNICEF. (Xinhua/Niu Xiaolei)

Singer Katy Perry reacts after being appointed UNICEF Goodwill Ambassador at the UNICEF headquarters in New York, US, on Dec. 3, 2013. Katy Perry will focus on improving the lives of the world's most vulnerable children and adolescents, according to the UNICEF. (Xinhua/Niu Xiaolei)

Singer Katy Perry (L) speaks during a panel discussion before being appointed UNICEF Goodwill Ambassador at the UNICEF headquarters in New York, US, on Dec. 3, 2013. Katy Perry will focus on improving the lives of the world's most vulnerable children and adolescents, according to the UNICEF. (Xinhua/Niu Xiaolei)

Singer Katy Perry (C) poses for pictures with teenagers after she was appointed UNICEF Goodwill Ambassador at the UNICEF headquarters in New York, US, on Dec. 3, 2013. Katy Perry will focus on improving the lives of the world's most vulnerable children and adolescents, according to the UNICEF. (Xinhua/Niu Xiaolei)

Singer Katy Perry attends a panel discussion before being appointed UNICEF Goodwill Ambassador at the UNICEF headquarters in New York, US, on Dec. 3, 2013. Katy Perry will focus on improving the lives of the world's most vulnerable children and adolescents, according to the UNICEF. (Xinhua/Niu Xiaolei)

Singer Katy Perry (R) poses with UNICEF Executive Director Anthony Lake after she was appointed UNICEF Goodwill Ambassador at the UNICEF headquarters in New York, US, on Dec. 3, 2013. Katy Perry will focus on improving the lives of the world's most vulnerable children and adolescents, according to the UNICEF. (Xinhua/Niu Xiaolei)