(I contributed that one.) It's kind of annoying because when you first see CycleGAN, you think, 'this is amazing! I can use it for anything, like turning faces<->anime!' And then you actually try and you realize your photo<->anime CycleGAN is just learning the steganographic encoding because the roundtripping is
too good ('wait, how does it reconstruct even the minor details of their hair so perfectly?') and so you wind up needing complicated regularization & tricks like "Improving Shape Deformation in Unsupervised Image-to-Image Translation" (
https://arxiv.org/abs/1808.04325), Gokaslan et al 2018, to get anywhere and the results aren't great. You
know the NN is intelligent enough to do it because the models are huge, it just refuses to because there's easier ways to meet the letter of the loss function but not the spirit...