The Rest of this amfAR Gala Took Place in Leg City

Sienna Miller, Serayah, and Rachel Brosnahan -- among a few others -- apparently didn't get the memo that the theme of this event was Your Left Thigh.

[Photos: Stephen Lovekin/Variety/REX/Shutterstock, Kristina Bumphrey/StarPix/REX/Shutterstock, Erik Pendzich/REX/Shutterstock, Matt Baron/REX/Shutterstock]