1:54 PM PT -- TMZ has obtained some video of Katy Perry's last residency show in Vegas -- and it looks like the stars on hand, including Celine Dion, were busting a move and having a blast. Check out this footage that shows the celebs who attended boogying down throughout the concert -- you can see Celine Dion bobbing to the music as Katy did her thing ... plus, Cameron Diaz and her husband, Benji Madden, were right behind getting their groove as well. So was Zoe Saldana, BTW -- so yeah, it was a packed house, and star-studded to the max. As for Meghan Markle and Prince Harry ... we're told they were also seated in the VIP section, but they were in a group of seats that were adjacent to Celine and co., so not really with them. Their night seemed to be a little more low-key ... with Meghan chatting up a woman she was sitting next to, and PH just kinda sitting there minding his own biz, somewhat aloof. Even when they were seen standing up with the others ... the couple just sorta stood there.
