Mr. Popper
Amanda
Mrs. Van Gundy
Pippi
Janie
Nat Jones
Mr. Gremmins
Kent
Franklin
Billy
Rick
Reader
Yates (as William C. Mitchell)
Young Tommy Popper (as Henry Keleman)
Tommy's Mom
Young Tommy Popper #2
Young Tom Popper, Sr. (voice)
Gremmins's Secretary
Town Car Driver
Daryl
Reginald
Tito
Freddy
Klaus (as Frank Cornei)
Arnold
Antarctic Friend (voice)
Animal Control Guy
Fish & Game Officer
Marine & Waterfowl Officer
Sanitation Officer
Random Man on Street
Nanny
Tavern Hostess
Fishmonger (as Angel L. Cabán)
Young Developer
Old Tom Popper, Sr. (voice)
Zoo Security Guard
Cop #1
Cop #2 (Quint)
Ice Skater (uncredited)
Gala Event Attendee (uncredited)
A Tramp / The Lone Prospector (archive footage) (uncredited)
Press Photographer (uncredited)
Gala Attendee (uncredited)
Fundraiser Guest (uncredited)
Student (uncredited)
Gala Guest (uncredited)
CoOp Board Member (uncredited)
Guggenheim Gala Attendee (uncredited)
Pulse Lounge Beautiful Girl With EyeGlasses (uncredited)
Pulse Lounge Beautiful Girl (uncredited)
Zoo Security Guard (uncredited)
Ballroom Dancer (uncredited)
Josh's Mom (uncredited)
Pedestrian (uncredited)
Tom Popper Sr. (uncredited)
Bar Tender (uncredited)
Security Guard (voice) (uncredited)
Penguin vocal effects (uncredited)
Fireman Dad (uncredited)