User blog comment:New Captain/X2: X-Men United "The Once and Future King" cameo/@comment-4190137-20120406084510

So there is a connection! You can put this in the bottom section of The Crystal Cave page, the section is called "Trivia".

And also, here is a link to the Crystal Cave episode if you want a more detailed comparison, http://merlin.wikia.com/wiki/File:Merlin_S03E05_The_Crystal_Cave