Many students of Daws Butler (the original voice of Yogi Bear) sent Dan Aykroyd tapes of Butler explaining how to do Yogi's voice. Aykroyd refused to listen to any of the tapes, preferring to do his own take on the classic character.
This is the first live-action adaptation of a Hanna-Barbera cartoon to be made without the assistance of William Hanna or Joseph Barbera, who passed away in 2001 and 2006 respectively.
When Justin Timberlake was younger and learning to sing, he imitated various cartoon characters, and so came in with a prepared Boo-Boo voice.