He was asking the question in response to this article about the apparent discovery of the emperor Caligula's tomb. The article explains how he was given the name Caligula - as a kid he used to accompany his dad (confusingly known as Germanicus) out to the battlefield, dressed up in a mini-soldier's uniform, including boots. The boots were known as caligae - caligula is a diminutive form meaning 'little boot(s)'. Interestingly the statue of Caligula which led to the discovery of the tomb is wearing a pair of these boots. The learned Rogue Classicum has more on the news, but is cautious (to put it mildly) about the authenticity of the discovery.
The article in the Sydney Morning Herald also trots out all the usual stuff about Caligula, as in this sentence:
After reportedly sleeping with his sisters, killing for pleasure and seeking to appoint his horse a consul during his rule from AD37 to 41, Caligula was described by contemporaries as insane.The article is decent enough to say that he only 'reportedly' slept with his sisters, but is pretty vague on who Caligula's 'contempories' might be. I'm not much of an expert on any aspect of Roman history, but the biographies of the emperors are generally not straightforward, and a lot of the most sensational stories often have to be taken with a fairly large grain of salt. In Caligula's case, the major sources of information about his life come from Suetonius and Cassius Dio, who are writing about 80 and 180 years respectively after his death. Wikipedia has a pretty good summary of the various sources and their reliability.
Of course, none of the sources portray Caligula as a saint, but he wasn't necessarily as insane and perverted as he's often made out to be, and in fact he seems to have been responsible for some genuine achievements during his reign.