During a visit to “The Ellen DeGeneres Show,” Kristen Wiig shocked us. She — and DeGeneres! — claimed not to know the words to “Let It Go,” but since they’re both humans with ears, we find that hard to believe. DeGeneres suggested they try to sing the hit from Disney’s “Frozen.” Thus began our favorite celebrity karaoke session of the week. Bonus points to Wiig for dropping this knowledge: “Kids don’t know what fractals are.”