Early in the film, Alvin (Paul Rudd) happens upon the charred remains of a home and discovers an old lady in a pink sunbonnet sifting through the rubble. This woman is played by Joyce Payne, who has had no prior acting experience, and the rubble she is sifting through is the actual remains of her old house. David Gordon Green and his location scouts simply happened upon her and asked if they could put her story into the movie.
The trivia item below may give away important plot points.
At the end of the film when Alvin is talking to the old woman in German, the subtitles translate 'Would you like to join us on our adventure?'. What he's actually saying is: 'Would you like to join our avalanche?'('Willst Du bei unserer Lawine mitmachen?').