Aconcagua, to the planes, is the most dangerous mountain to be near. Pedro tried to avoid him while getting the mail and almost got hurt. Pedro, out of gas, survived and made it back home with the mail.
A mountain inspired by Aconcagua can be seen in the comic El Kid Pampeador, of the Italian Disney comics authors Guido Martina and Luciano Bottaro (code INDUCKS I TL 219-AP), but it isn't explicitly mentioned as Aconcagua.
In the real world, Aconcagua is the highest mountain in the Americas at 6,962 m (22,841 ft). It is located in the Andes mountain range, in the Argentine province of Mendoza and it lies 112 kilometers (70 miles) west by north of its capital, the city of Mendoza. The summit is also located about five kilometers from San Juan Province and 15 kilometers from the international border with Chile. It is the highest peak in both the Western and Southern Hemispheres. It is one of the Seven Summits (the highest mountains of the seven continents).
It is not clarified if Aconcagua is supposed to be an anthropomorphic mountain (quite like Uku from the short Lava), or if the scary face that can be seen on the mountain is just an hallucination from Pedro, like the Forest Trees from Snow White and the Seven Dwarves.