She just exchanged "I do's" but Reese Witherspoon was spotted on the arm of another man in Sin City last night! Not to worry, the guy in question was Witherspoon's Water for Elephants co-star, Robert Pattinson, and the duo traveled to Las Vegas to present an award at the 2011 Academy of Country Music Awards. (Star couples like Ryan Seacrest and Julianne Hough and Nicole Kidman and husband Keith Urban did offer up some PDA at the ACMAs.) Also taking place over the weekend was the family-friendly Kids' Choice Awards, where Selena Gomez and Justin Bieber took home his-and-hers awards. See more photos from the weekend’s hottest parties in the gallery.