I can't remember whether it was two or three decades ago that I saw my first "Shit Happens" T-shirt. There are many variations of the list, but they're all about the various religious views of why shit happens. There are numerous listings on the web. I haven't checked to see which is the most complete. This one, from the infamous journal Maledicta (Volume 12, 1996), claims to be complete:
The Complete "Shit Happens" List
Some of these are quite funny. Note, thought, that the first one listed here is also the first one you will see on all the T-shirts, namely: "Taoism: Shit happens." And seriously, that's all there really is.