You see, when a mommy and a daddy love each other very much it can make Cthulhu jealous. When that happens, Cthulhu replaces some of the father's DNA with his own to create a monster baby. Most of the time they eat their parents or run away, but sometimes the child has enough harmony with it's parents that Cthulhu will sometimes drops by for Christmas and make some awkward conversation with its new relatives.

100% Log
The Binding of Isaac: Afterbirth (Except 1001% because it's coded dumb)
Cuphead
Hexcells/ Plus/ Infinite
Celeste

Crash N Sane Trilogy
Crash 1: 105%
Cortex Strikes Back: 102%
Warped: 0%

3D Mario Platformers
Super Mario 64: 120/120
Super Mario Sunshine 120/120
Super Mario Galaxy 120/240
Super Mario Galaxy 2: 242/242
Super Mario 3D World: All Stars, Stamps, and Flagpoles
Super Mario Odyssey: 0/999 Moons, 0/40 Costumes, 0/1000 Purple Coins, 0/52 Enemies

Games I'm close to 100%
Donkey Kong Country 2: 99%