Stewie appeared in '' Bones '' , eventually revealed to be the result of FBI Special Agent Seeley Booth 's ( David Boreanaz ) brain tumor . Seth MacFarlane wrote all of Stewie 's dialog for the episode . The character appeared in a Coca-Cola commercial during Super Bowl XLII , he and Brian appeared in a commercial for Wheat Thins , he presented a musical number at the 59th Primetime Emmy Awards with Brian , and he appeared at the 62nd Primetime Emmy Awards . He appeared on the December 21 , 2009 episode of '' Late Show with David Letterman '' to present " Top Ten Things You Do n't Want To Hear From Your Child . " There is much debate over which characters in '' Family Guy '' can understand Stewie . In an interview , MacFarlane said that everyone can basically understand him , but they ignore him or just think to themselves " oh how cute " when he talks . However at the 2011 ComicCon panel , he compared this to Wile E. Coyote in the old '' Merrie Melodies '' cartoons . MacFarlane went on to say that Brian always hears Stewie , and more recently so does Chris , but the writers usually strive for Peter , Lois , and Meg not to hear him . Once Stewie leaves the house , the question of who can hear him depends very much on the story . MacFarlane also states that these rules can be broken for the sake of comedy , so this could change from one episode to another . In " Inside '' Family Guy '' " , Peter apologizes to the family , to which Stewie comments : " Oh that 's nice of you to say " . Peter replies : " Thank you , Stewie , who I can understand " , referring to the ongoing discussion whether or not family members , other than Brian , are able to understand him
59th Primetime Emmy Awards
59th Primetime Emmy Awards
Stewie Griffin