It does happen cockroach. It's one of nature's more frustrating experiences, as being tumescent is not exactly condusive to the process of urination. This is why there are splashes on the seat.
GS -I have had similar experiences, but I had a terrifying dream a couple of nights ago. I was in bed with a young lady whom I'm considering finishing with (this isn't callous, just one of those things), and I dreamt that I told her i loved her. At the same time, she woke me up by rolling over and hugging me, and I was left thinking - Sh*t. Have I just said that out loud??
I still don't know, and it's a very hard thing to explain or take back.