The actors who played married couple, Daniel (Matthew Macfadyen) and Jane (Keeley Hawes), are husband and wife in real life.
Frank Oz once said that it was impossible to make Peter Vaughan laugh on the set because he was so deeply into the crotchety character of Uncle Alfie. He was the only principal actor to refrain from "corpsing" throughout, thus there was no footage of Peter cracking up to use for the closing credit montage.
According to Alan Tudyk the inspiration for his 'stoned' performance came from a memory from his teenage years when he once saw an intoxicated teen perched naked on top of a picnic table. He mimicked the same weird pose during his nude scene on the roof.
Originally the character of Peter wasn't written to be a dwarf. This change was made after Peter Dinklage auditioned and the role was re-written for him.