Basically, in a word, Caretaker.
Lots of Friends with Caretaker. Lots of Critter Friends.
Its Mane Character, Fluttershy (boosted) x1
~ ~ ~
The synergy is simple. Although the Caretaker ability cannot be stacked (a character with Caretaker will only ever get a +1 bonus regardless of how many Critter Friends accompany it), numerous characters with Caretaker are cumulative.
If you had 3 characters with Caretaker at a problem they would gain 0 power. Play or add only 1 Critter Friend, they each power-up by +1, totaling (in this example) +3. And that bonus is for their individual powers, Scoring Phase, Problem Faceoffs, and Troublemaker Faceoffs!
~ ~ ~
The only shortfall this deck would seem to have is an apparent inability to effect or control your opponent.
But with cards like Fluttershy, Guidance Councilor
and Mr. Beaverton Beaverteeth, Dam Builder,
this can be changed, dismissing opponent's resources and robbing them of their Action Tokens!
Of course this deck (unless severely modified or rebuilt) will still have its Orange powered cards which can come into play.