Elementalist
I write the alternate version of that scene that may or may not ever be shown to anyone but is here for my deranged mind to see.
Since the program I'm using for writing allows me to add a bajilion of scenes, move them around however and whenever I want, and then decide that half a bajilion of them aren't to be included in the output file and have them not be included, I don't have any problems with doing the above.
Roll with it. If comedy comes easier to you than drama, then embrace the comedy.
Write both scenarios and keep them. You can tag them if you must.
When you're editing your work you may find that the more humorous tone works better so you'll use that instead. Or perhaps you'll see that humour doesn't really work in your story so you'll remove it entirely. Either way, having both will give you some perspective.
I'll be blunt and come right down to the point; what do you do when you're visualizing a story and your mind keeps putting in jokes and humor in places where you don't want them to be? Like when you end up imagining a joke being put into scene that you wanted to be taken seriously.