Associated to a Thurston map f : S 2 → S 2 with postcritical set P are several different invariants obtained via pullback: a relation S P f ←− S P on the set S P of free homotopy classes of curves in S 2 \ P , a linear operator λ f : R[S P ] → R[S P ] on the free R-module generated by S P , a virtual endomorphism φ f : PMod(S 2 , P ) PMod(S 2 , P ) on the pure mapping class group, an analytic self-map σ f : T (S 2 , P ) → T (S 2 , P ) of an associated Teichmüller space, and an analytic self-correspondence X • Y −1 : M(S 2 , P ) ⇒ M(S 2 , P ) of an associated moduli space. Viewing these associated maps as invariants of f , we investigate relationships between their properties.