S(K(SII))(S(S(KS)K)(K(SII)))

I had already selected this request as my 40th while doing the 38th, so when I came to the 39th – which was also my first request vector of Applejack (!) – I planted a title that would lead in to this picture's title. S(K(SII))(S(S(KS)K)(K(SII))) is the Y combinator expressed in the SKI combinator calculus, which recursively applies itself infinitely to the following symbol: Yg = g(Yg). This recursion is also present in my own style of vectoring, reusing and adapting parts from my own previous vectors where possible; I flipped Fluttershy's and Pinkie's strokes and used them for Rarity's and Applejack's strokes respectively, among others. Thus, when I streamed this on my Picarto channel I breezed through the middle four ponies in one sitting because I knew where to toss the backreferences.

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