In TES Oblivion, after becoming the Grand Champion of the Arena, you meet an Adoring Fan.
In TES Skyrim, inside of Cicero's Journal Volume 1, you find that he posed as a fan of the Arena in the Imperial City.
In fact, at the bottom of the Adoring Fan page in the Trivia section, it says exactly what I said about the journal, but no reference to how he did it, who he was assassinating or when it was.
TES Oblivion takes place at the end of the Third Era (which lasted for 433 years), whereas TES Skyrim is based 201 years into the Fourth Era.
Was Cicero really there? How did he survive 200+ years?
Best Answer
He wasn't.
The passage in Cicero's journal is probably a reference to the adoring fan from Oblivion but it does not mean Cicero was that adoring fan. There have been many arena champions over the years aside from the Hero of Kvatch and many would have attracted fans.
Cicero's Journal also includes the dates of his assassinations. His journal states he completed the arena contract in 4E 187- only 14 years before the events of Skyrim. It is theoretically possible the Hero of Kvatch survived and was somehow still the arena champion (if s/he was an elf or a vampire for example) but this is a moot point- Cicero was not The Adoring Fan.
It's also worth noting that the adoring fan in Oblivion looks completely different, sounds completely different, acts completely different and is a completely different race from Cicero.