Ryan Reynolds as Jerry Hickfang / Mr. Whiskers (voice) / Bosco (voice) / Deer (voice) / Bunny Monkey (voice)

Gemma Arterton as Fiona

Anna Kendrick as Lisa

Jacki Weaver as Dr. Warren

Ella Smith as Alison

Paul Chahidi as Dennis Kowalski

Stanley Townsend as Sheriff Weinbacher

Adi Shankar as John

Sam Spruell as Dave

Valerie Koch as Jerry's Mother

Gulliver McGrath as Jerry (12 years old)

Paul Brightwell as Jerry's Stepfather

Alessa Kordeck as Sheryl

Michael Pink as Jesus

Ricardia Bramley as Sheila Hammer

Alex Tondowski as Tom