Take a “g” , “s” and “t” from “nuggets”, take an “a” from “McDonalds”, an “r” from “from” and an “e” from “piece”. Swap the letters around, that spells Gaster
SCP-447 is a ball of slime, you know what else is a ball of slime? Moldsmal. Moldsmal is found in waterfall (and ruins but that’s not relevant) which is where the Gaster room is located