The Canadian actor and singer Maisy Stella stars alongside Aubrey Plaza in “My Old Ass.” It’s a new coming-of-age movie about a teenager named Elliott who comes face-to-face with her 39-year-old self during a mushroom trip on her 18th birthday. Maisy joined guest host Talia Schlanger to talk about her big-screen debut, what it’s like playing someone going through a major transition, and how she manifested her role in this movie.