If you're ever thinking to yourself, "self, I'm kinda hungry.  I think I want Mac and Cheese, but I need some more protein than that.  Maybe I'll add some tuna to it and see how it is," let me offer this advice:

Be prepared for it to taste....odd.  It's not exactly bad, but everything about it just kinda seems a bit off.  I wouldn't really recommend it (hot dogs work better), but I wouldn't tell you to avoid it either.

I guess you can try it for yourself if you really want - at the very least, it's an interesting experience...