After Brian answers a science question correctly, Stewie says "Check out the big brain on Brian". In Pulp Fiction, after asking a math question, Jules (Samuel L Jakson) says "Check out the big brain on Brad"
Bertram says "so, Stewie invented a time machine," a la old Biff's line about Doc Brown from BTTF2. Also, Stewie's letter delivered by The Vatican at a specific time to assure Brian he's alive and where to find him. Joe Flaherty from this movie delivers the letter.