Little Romulus was installed in October of 475 AD, after Julius Nepos, who himself had been recently emplaced by the Eastern Emperor, was deposed. Julius Nepos had made three simple mistakes: first, he thought he new how to rule, second he appointed a Barbarian as his military commander-in-chief, and third, he relied on the Eastern Emperor to keep him in power. When the first mistake was revealed, Orestes, the new barbarian commander-in-chief and the father of Romulus Augustus, chased Nepos to Ravenna (by then a sometimes capital of the West) and then completely off the peninsula to Dalmatia. The Eastern Empire said it was all illegal but did nothing to reverse the situation.
So who was this Orestes who put his fourteen-year-old son on the Western Imperial throne. You're not going to believe it, but it's true: he was a former Staff Assistant to Attila (yes, the Hun!) Why, you might ask, did Nepos replace the previous "Master of Soldiers," a Patrician from Gaul named Ecdicius with Attila's staffer? Nobody knows for sure, but it certainly was a dumb move worthy of the late Western Empire.
The reign of Romulus Augustulus was short -- only ten months -- and not even long enough for his dad to establish a lasting bogus lineage of the Orestean family. And, as could be expected, the reign had a bloody end. Another barbarian, named Odovacar (or Odoacer in some sources -- long assumed to be a Goth, but called a "Skyrian" in contemporary accounts) showed up at Ravenna in mid-476 AD with a strong force of mutinous soldiers from Orestes' own army. Odovacar quickly defeated and executed Orestes and the rest of his clique. Little Romulus was spared because of his tender years and was sent to live with relatives as a virtual prisoner on an imperial estate near Naples. It is recorded that he and his mother (identified only by the generic "barbarian female" name Barbaria) later founded a long-lived and successful monastery in the area. The only other notice of the later life of Romulus is that he twice had to renegotiate with Theodoric, Odovacar's Ostrogothic successor, the pension that Odovacar had granted him.
Neither Odovacar nor Theodoric (who killed and took over from Odovacar) ever claimed to be Emperors or anything other than kings in the areas they ruled, which never really amounted to more than their part of Italy. Some sources claim that (as part of the arrangement that Odovacar made for Romulus' survival) Romulus, in his final imperial act, formally abdicated by letter in favor of the Eastern Emperor, and that Odovacar subsequently sent the Imperial regalia to Constantinople. This is shadowy stuff, however, and it's just the kind of propaganda that Justinian, who was Eastern Emperor in the mid-530's AD, would have cooked up to justify his "reunification" of the Empire. Justinian sent Belisarius, who established a few garrisons around Italy, and then claimed that all of the former Western Empire was reunited with the East, under Justinian of course. But neither Justinian nor his successors ever came to Rome. Charlemagne showed up in Rome in 800 AD, and we just know that the few natives left in the city must have laughed behind their hands at the antics of the pretender from that hick town, Paris.
Last Emperor Internet links:
From De Imperatoribus Romanis: http://www.roman-emperors.org/auggiero.htm. Use the link at the bottom of the page to find info on many other Roman Emperors
Romulus Augustulus: http://www.britannica.com/eb/article?eu=86060&tocid=0&query=augustulus&ct=
Barbarian Migrations: http://art1.candor.com/barbarian/
P.S.: 1. Some "experts" say that Julius Nepos was the last "real" Roman Emperor: he was appointed by and was a supposed relative of the Eastern Emperor of the time. Nepos continued to "rule" in exile and may have actually outlived Romulus. Another deposed Western Emperor, Glycerius, was also still around, living a powerless life as the Bishop of Salona. Experts go round and round about who was real and who wasn't among the last bunch of emperors, totally ignoring the fact that the "imperial" lineage they support was riddled from the beginning with bastardy and with purely political adoptions -- there never was a real imperial family. And after everything is said and done, it was Romulus Augustulus who was the last to sit in the chair.
2. Ancient Romans thought that pretty much anyone outside the Empire was a barbarian. The word "barbarian" came from barba, the Latin word for beard. Or maybe the other way around: perhaps "bar, bar, bar, bar·" was what Romans heard when the wild bearded tribesmen spoke. People who always said "bar, bar, bar, bar·" and had beards were barbari or "barbarians" and the Latin word for beard became barba. On another hand, maybe the first "barbarians" the Romans met were Riff Mountains Berbers of North Africa. Or maybe the other way around: the Berbers might have acquired their tribal name by being bearded or barbarians. It just goes to show that etymologists can get just as confused as the rest of us.
3. Ancient Roman thinkers and their successors until today have compared the barbarity of the "barbarians" to that of the Romans, and in many ways the barbarians have come out better. No barbarian tribes did as much damage, stole as much loot, took as many slaves, killed as many enemies in battle or in post-battle slaughter as did the "civilized" Romans. And none of them practiced anything like the ritual public killing of the amphitheaters -- at least until they had been taught and "civilized" by the Romans. Barbarians might kill thoughtlessly, or in the heat of battle, or before their battle-boiled blood subsided, but only the worst of them took home hapless prisoners to slaughter in front of the wife and kids, and never on the vast scale that the Romans did.