I don't have my copy of Swan's handy, but: everybody and everyone takes the singular Everybody is / Everyone is happy on Friday afternoon. People can be thought of as the plural of person and takes the plural form People are addicted to their mobile devices.

Everybody is: "Everybody is going to show tonight" Everybody is used as a singular noun in this context If you had multiple or plural nouns, it would be 'are' "Sarah and Michelle are going to the show, so I'm definitely going too"

Everybody is, people are... ;^)

Alot of people in America uses "everybody is" insted of everybody are...but it is not a problem to use everybody are.