In the storeroom the Mets logo on Apu's shirt temporarily turns into a black logo shape.
Whenever new states join the Union, the additional stars aren't added to the American flag until the next Independence Day (July 4th), and New Mexico and Arizona both became states between the same two Independence Days, so the flag changed directly from 46 to 48 stars and hence there was never an official 47 star version.
When Groundskeeper Willie says to the children, "You want to pick on immigrants? Then pick on Willie," there appears to be two Ralph Wiggums in the crowd of children.
Apu doesn't get deported because he takes the citizenship test and becomes a legal citizen; however, Proposition 24 says nothing about "illegal" immigrants. It merely states that all immigrants are to be deported.