Last week, holiday parties were in full swing — kicking off with ASmallWorld’s tenth annual winter weekend in Gstaad, which included an elegant gala hosted by Carey Mulligan. Stateside, celebs entertained themselves by taking selfies with Santa: Nicole Richie hung out with him at the Baby2Baby Holiday Event in L.A., while back in New York, Zac Posen sat on St. Nick’s lap at the Brooks Brothers party with St. Jude’s. People hosted its annual awards Thursday night, where the magazine unsurprisingly named Kate Upton the sexiest woman of the year. (She celebrated with Pharrell, Gwen Stefani, Jennifer Aniston, and J.Lo.) Suki Waterhouse traveled to Seoul for Burberry’s Beauty Box party, Justin Bieber attended the launch party for Will.I.Am’s new smart band, and Amy Adams hung out at the after-party for the premiere of Big Eyes. Click through the slideshow for these and more highlights from the week’s biggest parties.