You can say..... I saw someone eat your pizza.......or I saw somebody eat your pizza. There's no difference. Another example is..... Did anyone go to the concert? Did anybody go to the concert?
Everyone here is crazy.... Everbody here is crazy.... (some more than others
Noone came to my party so I ate all the food and drank all the wine by myself. Nobody came to my party so I ate all the food and drank all the wine by myself.
There is no difference. You can say Everyone OR Everybody without any difference in meaning. It depends on you. There are no grammatical rules to say that one is better than the other.