Man, you kids don't remember Ghostbusters Ectoplasm, or the TMNT "ooze" do you? Ectoplasm came in all kinds of colors - Purple, Red, and Blue for example - it had its own sub-line of toys (one for Slimer, of course).. THAT stuff was MESSY.. and it smelled horrible if you left it to dry out. Oh, God Forbid you let it dry out on the toys, you weren't ever getting that stuff off.
Oh, wash it? And re-hydrate the slime? Makes it smell worse and makes it almost like paste.
...dear Sweet Zombie Jesus, I'm old.