Heart and Souls (1993)
Hal says, "What am I, in 'The Twilight Zone' here?"
When the bus driver (played by David Paymer) appears and says "I need one of you now", after Milo has completed his earthly task of returning the stamps - he says "Hello!?" - this is a reference to his character in Crazy People (1990) in which he plays a mental patient called George whom only says the word "hello".
The way Charles Grodin sings National Anthem in the same way Baldo Del Ponte sings it before the Cubs game watched by Charles Grodin and James Belushi in Taking Care of Business.
An episode is seen playing on TV as Penny leaves for work.