The standards by which we judge humor differ depending on whether we are witnessing an actual occurrence or reading a work of fiction.
Something that makes you laugh in real life does not necessarily translate into a good comic unless some details are altered or exaggerated.
Also, you have very limited space in which to set up the premise of your joke and deliver a punchline.
The audience doesn't know you, so in order to frame your narrative in a context they'll understand, you have to utilize universally recognized symbols.
You used the picture of the crazy old scientist guy to represent me! That's it, no sex for a week!
And most importantly, always write under a pseudonym.
