Deadman Wonderland, Karneval (TV) Recommendations
Both of these anime have a cheery circus motif that hides darker elements underneath. Also, both have the innocent white-haired, red-eyed child character (Shiro in Deadman Wonderland and Nai in Karneval).
-Both have a circus/amusement park theme.
-Both include mutants/hybrids.
-Both are quite dark, although DW is more explicit.