My friend wanted me to research something or ask a doc for him, as he is way shy and would be mortified to go to his GP and say anything, unless he knew it was serious.
Today when he went to urinate, he says that he had a stream of what looked like thick mucus or very thick semen hanging from his urethra opening.
Yuck, I know. Quadgop, anyone, thoughts?
Not to alarm anyone, but one of the symptoms of gonorrhea is a mucoid discharge from the urethra. Emabarassment aside, I’d have your friend visit his doctor. It’s always better to be on the safe side.
I won’t get specific (like saying “gonorrhea”) because lots of things can cause infections, but yeah, that’s most likely what it is - some sort of infection. Of course, I am not a doctor (though this post should keep the thread where the docs can see it).
Not enough info to make much of a diagnosis. It could be anything from a seminal remnant in the urethra to balanitis to something really unpleasant like gonorrhea. If there is any pain, discharge, or a recurrence of this phenomenon, friend should see a doctor.
Oh sure, Qadgop. When I misspell your name I get called Q.U.E.D. or somesuch. 
Was it before, after or during urination?
Has the person been sexually active?
Any pain or discoloration?
Ok, more info. He says there is no pain. He noticed this before beginning to urinate. He hasn’t had an orgasm in a week or more, and is monogamous.
A whole week?
Was this the first pee of the day?
Possible wet dream.
seriously.
That’s 'cuz I expect more out of you! 
Because of my medication I occasionally suffer the same problem: supressed sex drive and supressed wet dreams. After urinating I get this weird quasi-orgasmic feeling like I’m going to ejaculate and you know the rest.
Before going on meds I would masturbate once a week to avoid having a wet dream.
I recommend more masturbation between partner-based sex episodes.
There is no charge.