Ellen DeGeneres arrives in Jennifer Lopez's Las Vegas green room in that green Versace Grammys dress Lopez made famous.
Decked out in the singer's green Versace gown made famous at the 2000 Grammys, DeGeneres barged into Lopez's dressing room to prep for her self-appointed role as J.Lo's understudy for her "All I Have" show in Sin City.
"Thank you for letting me -- for asking me to do this -- well, you didn't ask me, I volunteered, so thank me for volunteering," DeGeneres said to Lopez.
Lopez had to explain to an eager Ellen that "there are no understudies in these types of shows," but DeGeneres was not taking no for an answer.
"You're in denial," DeGeneres said.
The two then warmed up their vocal chords and did some stretching before reaching a compromise: Lopez would give "Lil Ellen" a shoutout during the show.
See how it all goes down in the videos below.