The Cramp Twins/Headscratchers

• What's with those little lines outside everybody's outline?
  • It's just how the art style is. Kind of like how the lines around the characters in Ed, Edd 'n' Eddy are all squiggly or how Teen Titans is drawn in a psuedo-Anime style.
• One has purple skin. One doesn't. How does their mother mix them up?
  • Color Coded for Your Convenience, maybe?
    • That doesn't seem to be the case, as in one episode, Wayne spray paints Lucien's skin to resemble his.
  • She's that stupid.
• Why are they called the Cramp "Twins"?They don't look like each other at all. Also, why does the mother allow junk in the house, but not dirt/animals?
  • They are non identical twins.
    • The opening shows them both in the same womb, how are they not twins?
    • They're twins, but non-identical twins. Lucian even points this out explicitly ("we're totally non-identical") in an episode where a twin researcher comes to live with them. Not all twins are identical.