Why Slithe doesn't look like the generic Reptilians
This issue has been raised before, but I don't think anyone's come up with an answer. I have.
Rataro claims that Slithe, when under his command, was a cook - which Vultureman also mentions in another episode. You've heard the mantra "never trust a skinny cook"? Well, I guess Slithe's cooking could be trusted implicitly.
And I say this as a slightly overweight fellow myself, whose cooking has always been highly appreciated!