The first is that of the "Undefeatable Troublemaker".
Wild Manticore (troublemaker) x1
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Sunny Smiles, Iconic Friend power-ups!
Sunny Smiles, Iconic Friend x3
The key character in this synergy is Sunny Smiles, Iconic Friend. All these other cards - troublemakers, problems, and friends' abilities - power her up every time they force an opponent to discard.
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And finally, there is a simple, if not overly powerful, synergy with Cherry Jubilee and the Hard Hat resources.
(The Hard Hat resource - giving a Friend Stubborn, although not useless, isn't particularly powerful in a deck with Stubborn characters - can be put to good use played (repeatedly) on Cherry Jubilee, powering her up to +3 4 power in total).