I'm going to assume that the Trivia section contains a lot of information from the manga that was not in the show (at lot of stuff dealing with Huey and his followers).
It's disappointing that they basically did 1 and 1/4 seasons when it seems they had a lot more story they could have done.
The original 13 episodes cover approximately 2 1/2 light novels, so really they crammed a lot of story into the relatively short running time. Unfortunately the series didn't do well in Japan, which is probably why there were no further seasons despite there being more novels to draw from.
"You always know where the X-Men have been, because it's always on fire."
- Pete Wisdom