Mulligan:

1. Undertaker - Mad Scientist and Nerubian Egg are both Deathrattle cards. Don't play this on Turn 1 as Thaddius will use Lightning Bolt. It's safer to use this on Turn 2 as he will have lower probability to have another Lightning Bolt card.
   
2. Mad Scientist - This can be a fun way of duplicating other Deathrattle cards on the board. Mad Scientist is meant to die - +1 attack for Undertaker and this will automatically put Duplicate on the battlefield.
3. Nerubian Egg - Apparently, Thaddius has poor IQ. He will still make use of Polarity Shift even though Nerubian Egg has ZERO attack. Use this to your advantage. If Deathrattle is triggered with Duplicate in the playing field, say hello to two more Nerubian Egg cards.

I won't go further as doing so may KILL the FUN. :D The above guide will suffice for you to survive Thaddius on Normal mode. Good luck!

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