Graphical representations of the Ising model have been tremendously successful for both simulations and rigorous results. These representations are coupled to each other using the uniform even subgraph operation, which is invariant under XOR. Using intution about the ground state of the toric code this trick enables simple proofs of equality of critical points of the loop O(1) and Ising models and exponential decay for the two-dimensional near-critical model. The scaling limit of the latter is famously conjectured to be related to the exceptional Lie Algebra E_8.
Joint work with Ulrik Hansen, Jiangping Jiang and Peter Wildemann.