Read the comic here.
Donut's humor falls flat because, as we all know, Castle is one of the HUGE themes as far as fans are concerned. Curtis scores a point in that many on-line LEGO communities look down on the Bionicle line, despite the ginormous fanbase it enjoys. They really are two seperate worlds most days.
By the way, I bet Curtis is a big fan of the long-vanished Western theme.
Of course, you have to start talking about LEGO Webcomic authors before you get *really* niche.