'Thor: Ragnarok' and the importance of movie stars

Our critics review “A Bad Moms Christmas,” starring Kristen Bell, Mila Kunis and Kathryn Hahn; “Thor: Ragnarok,” with Chris Hemsworth back as Thor, and directed by Taika Waititi of “Flight of the Conchords;” and “Lady Bird,” about the relationship between a mother and her strong-willed teenage daughter.