Disclaimer: I own only this possibility for Conan's future.
Hey, Manzanita, you mentioned something about payback. How's this? (grins)
(Edit 11/05: As per my new policy, anonymous reviews get answered in my profile.)
In retrospect, Conan probably shouldn't have gotten impatient and tried to work on the cure on his own. Just because he was a genius when it came to detective work it didn't mean he would automatically be a genius chemist as well, especially not with such powerful and complex compounds.
If nothing else, he should have at least told Agasa what he was doing.
But as he struggled to escape his suddenly far-too-large clothes, a piteous mew escaping him as his fluffy gray and white paws proved ineffective, all that he could think was that this wasn't supposed to happen.