Mariah Carey may not know Jennifer Lopez , but she does know John Legend.The pop diva was performing in Las Vegas when she invited Legend to join her on stage. This, as you can see, proved to be way too overwhelming an experience for wife Chrissy Teigen to process."Mariah pulled @johnlegend on stage at her Vegas show and as a lamb, I have never been so happy," Teigen later told fans. "There is no Mariah song I don't know the words to and I may have cried but whatever I LOVE YOU @MARIAHCAREY. Thank you for this amazing night for me and my family!!"Let's roll the tape.