The diamond dealer Reggie phones, is called Doug. This is a reference to 'Snatch' 2000 in which one of the main characters is called Doug the Head, played by Mike Reid. Reggie then says he's calling his Hebrews in NYC, which, whilst not directly referenced, is likely to be 'Cousin Avi' - again, another character from 'Snatch' played by Dennis Farina.
The janitor at Groff Community College and at the church the Smiths' attend is the same person.
WILHELM SCREAM: Heard when the bus goes over the cliff.