 MacFarlane was cast as four of the show 's main characters : Peter Griffin , Brian Griffin , Stewie Griffin , and Glenn Quagmire . MacFarlane chose to voice these characters himself , believing it would be easier to portray the voices he already envisioned than for someone else to attempt it . MacFarlane drew inspiration for the voice of Peter from a security guard he overheard talking while attending the Rhode Island School of Design . Stewie 's voice was based on the voice of English actor Rex Harrison , especially his performance in the 1964 musical My Fair Lady . MacFarlane uses his regular speaking voice when playing Brian . The voice of Quagmire was inspired by fast @-@ speaking radio advertising spokesmen from the 1950s . MacFarlane also provides voices for various other recurring and one @-@ time characters , including news anchor Tom Tucker and Lois ' father Carter Pewterschmidt . 
