It is usually accompanied by: hasta atrás y cubierto de tierra. Como huevo de perro literally means "as a dog's testicle." Dog testicles are located at the very rear of the dog's body and, in the case of the street dogs that abound in DF, usually covered in dirt. Hasta atrás (lit. to the very rear) means wasted, utterly drunk. Cubierto de tierra (lit. covered by dirt) means that, being so drunk, the person has fallen to the ground repeatedly and gotten noticeably dirty.
Maclovio: Bueee...nass ...ochesss.
Venancio: Otra vez vienes como huevo de perro: hasta atrás y cubierto de tierra.
Maclovio: Ooood eve...ninnnn.
Venancio: You're hammered and dirty again.