Who says you need a man and a woman to sing a duet? Watch Reggie Ramirez channel both Lionel Ritchie AND Diana Ross by singing Endless Love at Philippines Got Talent in this YouTube clip.
... Glamamore/Mr. David lipsynch to With You I'm Born Again by Billy Preston and Syreeta at Circus Night at Trannyshack, 2006:
... and Mark James in Britains Got Talent, 2010 semi-finals, breaking both Elton John and Kiki Dee's heart in this fantabulous performance of Don't Go Breaking My Heart