Tenacious D heads back to prom at to support a worthy cause; Julie Benz shows off her pants at the "Bands For Beds" charity event; Kurt Russell and John Travolta are honored at the "Living Legends of Aviation" Awards; Joni Mitchell steps out for the opening reception of Alexander Yulish's art exhibition—clearly not everyone fled to Utah for Sundance this weekend, so check out the stars that stuck it out in L.A. in this edition of Last Night's Parties.