Do you have the problem to say for yourself "yep, that's my favourite (thing)"?
I actually have this personality problem too, either we are the just the braintards or everyone who can out loud say this is an extra aka NPC (le dehumanizing meme).
Anyways, I think the easist trick which almost always works to get a good fitting username is just as I presented first in this thread.
Can you grasp at least your favourite food item or do you can think about any food item (which is not copyrighted) that sounds interesting/somewhat funny to you?
Keep that one and add/change something on it, then you should have an username.
Personally, names emerged by this method have a "moe/cute" impression to me, but they should be fitting in the same position with any popular Youtuber, streamer, artist, etc.