Earth's flag is the flag of Earth. Referred to as "Old Freebie", it is an adaptation of the flag of the United States of America, representing the Earth as a whole in place of the stars of the 50 U.S. States. It is of the same proportion as the current U.S. flag, with the same number of stripes.
The roots for the nickname "Old Freebie" has never been explained. It is the custom of Earthicans to fly Old Freebie prominently on Freedom Day, a celebration similar to American's Independence Day.
Zoidberg ate the flag as an expression of his love for freedom, and was subsequently persecuted and then prosecuted. However, after playing a pivotal role in releasing Earth from the oppression of the Decapodians, Zoidberg receives a full pardon and is granted the right to eat the flag once again.