Colonel Alvarez is a colonel in the San Theodorian army who works as General Tapioca's Aide-de-Camp in Tintin and the Picaros. He is also in the league with Colonel Esponja, Chief of the San Theodorian Security Police, who is actually the Bordurian Colonel Sponsz and old foe of Tintin.
After General Alcazar reclaims power, it is unknown weather Alvarez was able to keep his position, however the original series suggests that he does. General Tapioca is referred to as "Ex-General" while Alvarez is still referred to as "Colonel". Since revolutions are common in San Theodoros, officers do not appear to be relieved of their positions even if the leader that they were serving was toppled.