.

[Curious Diode]

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[Wolf]

While I don't have a GCC myself, I do know from several other people that have them that they love to snuggle and many of them will snuggle in under a hand in exactly the manner you described and is shown in the pictures you posted. Many of them also like sleeping in those cozy huts for birds, as well.
While he liked the head scratches for a while, he sounds like he was really looking to go to sleep and so after a shot while it bothered him so he got up and stretched so that he would be ready to fly if needed( that would be instinctive) and then probably bit you to say stop it you are bothering and I can't sleep, put me to bed. This is probably not actually what he was thinking and it is anthrmorphasising some what to word it this way, but there is nothing to worry about in his behavior as far as I can tell. His actions are natural, normal and make sense.
I would consider what time of day this occurred at as well, because his actions suggest to me that you may have been keeping him up past what his bedtime should be. I don't know if that is the case or not, but just as a reminder your bird should normally be fast asleep right about dark or very soon after.

[Curious Diode]

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[Wolf]

If it was near to or past his natural bedtime, I feel that this would account for his aggressiveness.

[Pajarita]

Wolf hit the nail right on the head. Once the sun starts to set, their internal clock says: time for eating dinner and roosting on a full stomach (or, in their case, a full crop ). And they can be pretty assertive when it comes to their needs!

I suggest you try to keep him at a solar schedule and 'listen' to his natural biorhythms because it would not do for him to learn that he has to nip you hard for you to pay attention and do what he needs from you. I am sure you must have heard this a million times but parrots, been undomesticated species, do not adapt to us, we need to adapt to them... or pay the price for not doing it

[Kakariki]

For sure. Now that my greencheek has learned (actually, now that I learned and began the regime of proper bedtime), on the rare occasion that I do not say out loud...'time to snuggle the bunny" (that has been his thing, h has a wee fuzzy stuffed bunny he hides under at bedtime since I got him) and I atm late with it, he will fly to me and do a specific 'peeping' noise, and \I look at the clock or out the window and realize it is time to snuggle the bunnie. and he gives me a kiss goodnight and I put him and Crayola in and cover them. Jasper is 2 yrs, 2mesths old and I have had him since a babe. Conures are nippy by nature, but his are not harmful, just telling.

[shiraartain]

I'm actually a little jealous! My GCC will also cuddle under my hand. Then crawl inside my shirt or sit on my knee under the desk (the light doesn't reach there) and fall asleep. And when I try to extract him to take him to his cage....ow.

[Pajarita]

Well, of course you need to be punished! It's your darn fault the poor baby is been inconvenienced so rudely - you should have remembered to put baby to bed when he got tired.