"Ugh, gross!" Naruto groaned in disgust, covered in snake guts from the snake that swallowed him whole in the Forest of Death. "Well, now I have to find Sasuke and Sakura and get through this exam..." Naruto then noticed a scroll on the ground. "What's that...? It doesn't look like one of the scrolls for the exam..." Naruto opened up the scroll, and saw a seal, which instantly glowed and let out a bright flash of light.
When it subsided, Naruto noticed that he felt weird, as if he only had one section of a body, which was just one section without any limbs, butt, penis, or anything on his head (which seemed to be directly a part of his body, without anything like a neck separating them), except for two things sticking out where his eyes would be, which he could see through, and what he could best describe as feeling like a tail that was directly a part of the rest without any section in between. He was definitely shorter than before, which had already been a sore spot.
What happened to me!? Naruto cried out, although it came out as a bunch of squeaks, freaking out, as he used his replacements for his eyes to examine himself as he twitched around. I became a slug! I have to figure out how to turn back! Suddenly he felt odd, and started shifting, becoming larger, and reforming his missing parts, as his new ones vanished.
"I'm back to normal!" Naruto said with a sigh of relief, looking over his hands, and feeling himself over. "Could I do that again?" Naruto focused on becoming the slug again, and immediately shifted into the form. Ok, that's interesting... Naruto began. I wonder why my clothes vanish when I do this... " … and come back when I turn back to normal..." He shifted forms a couple of times, testing it, he. During this, he noticed an odd feeling, his mind drifting towards girls he's seen, and going into their vaginas as the slug form for some reason. He also found that he was naturally slimy, but was able to latch onto things with suction cup like things on his underside He shook his head. "What am I doing? I need to get back to the others!"
What happens? Note, for choice one, Orochimaru's Five-Pronged Seal doesn't work, as Naruto's body reflexively lets out slime before it settles that keeps it from sticking.