Kilroy (Doctor Who and the Warlord)
While a human companion to the Sixth Doctor was attempting to stop an attempted assassination of the Duke of Wellington in 1815 orchestrated by the Time Lord the Warlord, they came across a man wearing a Union Jack uniform in the Brussels forest. The man told them that they had three chances to guess his name, otherwise he would shoot them.
The companion indicated that his name was Kilroy, which was correct. Kilroy told the human that he wanted to assist them in defeating the Warlord. Kilroy gave the human a sonic lance recharge module then walked into the night, seeming to disappear. (NOTVALID: Doctor Who and the Warlord)
Behind the scenes
Kilroy is perhaps one of the most perplexing aspects of the 1985 text-game Doctor Who and the Warlord. Kilroy can only be found by following a very specific chain of directional inputs in the final arc (from Brussels Road: west, north, north, east, northwest, northeast, north, west, north, north). It is not currently understood how the player was meant to know the correct name, although it should be stated that the character is obviously a reference to the Kilroy Was Here "Meme."
Afer "Kilroy" drops the lance recharge module, he walks from the protagonist. The in-game text reads: "for a moment you think you can see right through him, but then he is gone." This implication, added to his knowledge of the Warlord, seems to indicate that Kilroy is not simply a random human. However, this is not expanded on.
In spite of the utter absurdity and obscurity of the character, speaking to him and getting his name correct are essential to beating the title.