OK, so you should really read that link b/c it's pretty short and very interesting. Here's the first couple paragraphs (I bolded the part I found most interesting):
The word “transubstantiation” derives from Latin – trans (across), and substantia (substance). The term is employed in Roman Catholic theology to denote the idea that during the ceremony of the “Mass,” the “bread and wine” are changed, in substance, into the flesh and blood of Christ, even though the elements appear to remain the same.
This doctrine, which has no basis in Scripture, first appeared in the early 9th century A.D., was formalized at the Council of Trent (A.D. 1545-63), and was reaffirmed at the Second Vatican Council (1962-65).
So one of the major things Catholics seem to really "enjoy" (for lack of a better term) is also a 'man-made' idea basically...Well, at least if you agree with what the link says.