Ryan Reynolds Cal / The Man Upstairs John Krasinski Bea's Dad / Marshmallow Cailey Fleming Bea Phoebe Waller-Bridge Blossom (voice) Louis Gossett Jr. Lewis (voice) Steve Carell Blue (voice) Fiona Shaw Grandmother Bobby Moynihan Alan Kim Benjamin Matt Damon Flower (voice) Emily Blunt Unicorn (voice) Vince Vaughn (voice) Sam Rockwell Guardian Dog (voice) Maya Rudolph Alligator (voice) Sebastian Maniscalco Magician Mouse (voice) Richard Jenkins Art Teacher (voice) Christopher Meloni Cosmo (voice) Awkwafina Bubble (voice) Jon Stewart Robot (voice) Liza Colón-Zayas Catharine Daddario Matthew Rhys Ghost (voice) Keegan-Michael Key Slime (voice) Bradley Cooper Ice (voice) George Clooney Spaceman (voice) Amy Schumer Gummy Bear (voice) Blake Lively Octopuss (voice)