Godzilla vs. Mechagodzilla
As of the film "Godzilla vs. Mechagodzilla", Anguirus tunneled his way to Japan and encountered Mechagodzilla disguised as the real Godzilla. Realizing it was an imposter, Anguirus fought Mechagodzilla, but had its jaw broken in a bloody display and forced to retreat underground. Despite this, Anguirus tore off a piece of Mechagodzilla's disguise and alerted Godzilla to the imposter's presence.