A moment in which, the server of dank memes, or indeed any server or group chat, starts talking about CP, for no apparent reason, the chat goes from shitposting to talking about legality and morals of Child porn.
(JohnEden was the username of a wierdo who said loli is ok)
Where Ocean, Yuuko, or Evoker say some sus ass shit that makes you wanna say "I hate it here". Much like Yuuko moment and Ocean moment the Xeno GC Moment is used in the same manor.
"Wow Ocean came in a hot pocket this sure is a Xenoblade GC Moment, lmao!"