Mad Scientist Interaction with duplicate secrets
Normally you can't play 2 of the same secrets at once.
However, let's say you have freezing trap already in play, and your deck still has 1 more freezing trap and no other secrets. If your mad scientists dies and triggers the deathrattle, would it cast the additional secret or just do nothing?
Solution 1:
"If the only Secret left in your deck is a copy of one you already have active, Mad Scientist will draw nothing at all."
-- Ben Brode, senior game designer on Hearthstone.