’I Want You Back’ co-stars Charlie Day and Jenny Slate take Vanity Fair’s infamous lie detector test. Does Charlie regret passing on the opportunity to play Charles Manson in ‘Once Upon a Time in Hollywood?’ Does he see the resemblance between him and NBA player Josh McRoberts? Does Jenny believe in ghosts? Does she think she is smarter than most people in Hollywood because she went to an Ivy League school? Can she do an on-the-spot Marcel the Shell voice?