Ebira is not a playable character in the game. The playable characters are:
* Godzilla
* King Ghidorah
* Mechagodzilla
* King Kong
* Rodan
* Mothra
* Anguirus
* Gigan
* Hedorah
* Kamacuras
It's possible you're thinking of another Godzilla game or a different monster altogether.
Do you remember any other details about the game you're thinking of? Knowing the specific game would help identify if there is a way to unlock a character like Ebira.