I managed to win with all three

A lot of it always comes down to if you can deal with a Pumpkin on turn 2.
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The Witch goes a lot smoother if you get a 4-mana Wild Growth and can start dropping big taunts early to preserve your face.

The Pirate you want to ignore your normal instincts. Throw your weapons at his face and sacrifice your minions for board control. It's a long fight, so your health is a crucial resource. Once you've gotten to stage 2, drop Cookie (Who should be pretty big by now) for the win.

The Cat...I got lucky. King Mosh off an Infestation. I tagged his second form with a Grevious Bite on an adjacent minion and instakilled it with Mosh.