I forgot about that Rats are actually pretty good if they are not part of the supply.
So there are 2 possibilities:
A) Have "nice Rats" and forget about the Attack.
Pied Piper (Action) $3
+1 Action
Trash a card from your hand.
Gain up to 2 Rats from the Rats pile.
B) Add Rats to the supply and make them evil:
Pied Piper (Action-Attack) $3
+$2
Each other player gains a Rats.
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In games using this, if Rats are not in the Supply, add Rats to the Supply.
I guess the latter is less promising because the Rats pile does not scale with the number of players.
Printer (Action) $4
+3 Actions
+$1
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When you discard this from play, if you have played at least 3 Actions this turn (including this), you may trash this. If you do, gain a Library from the Library pile.