1 Prof. Jones: What's C++?
1 Merlin: Oh, it's a thing from the future. You wouldn't know about it.
2 Prof. Jones: But, that's the answer! You enchanted the Siege Perilous, right?
2 Merlin: Of course.
3 Prof. Jones: You're Merlin! You live backwards in time, so the Siege will spare those who have already found the Grail, not those who will later find it.
4 Merlin: Ooops. Sorry, I better run! Have to go check on Galahad!

Some readers did point out the anachronism in Merlin mentioning C++ in strip #3694. I knew that when I wrote it, because it was a deliberate setup for this resolution.

The TV Trope of characters living in reversed time is named, appropriately enough, Merlin Sickness, since the canonical example is Merlyn from T. H. White's 1958 version of the Arthurian legend, The Once and Future King, dating back to book one of the cycle, The Sword in the Stone, originally published in 1938. This aspect of Merlin's character has become something of a standard in newer works, although White invented it and it was not part of more traditional Arthurian legend.

It's cool what you can do with a well-placed bit of anachronism, isn't it?