This may not be a new exploit, or an exploit at all, but I have a hunch. When you shoot Glooper Blooper with FLUDD his eyes turn pink, the same way as if you pull his nose to the damage point, what if you shoot him with FLUDD, then immediately grab his nose, after you grab the nose his eyes won't become white until he's done being hit. I would test it out, but I don't have SMS.

The only way to damage gooper blooper is to pull his nose to a certain length, his eyes are just a visual thing. Also, if you try to grab his nose while there's still goop on it, Mario slips off of it.