Wow, there is some great information in this thread!
I have a GCC named Bubba. He is a re-home and when we got him he was 2.
He is
super high energy and is very mischievous. He is fearless; he will bully other animals (in his first house apparently he would chase their boxer) and he will bully other people so I have to keep him in his cage when we have visitors (he is fully flighted).
He was very nippy when we first got him but he was in his 2s and from what I understand birds (especially conures) are known for nipping and biting in that stage of development. We did our best to ignore the bites and nips and now that he's a little older he rarely bites but he still nips a bit.
He is extremely demanding. He wants human attention and interaction almost all of the time. The only exception to this is when he's taking a nap or after he's had a bath and he's wet. He has lots of toys and he plays with them occasionally but his main focus is human attention. He wants to cuddle constantly and will cuddle your ear, neck, arm, or hand. Sometimes if I am busy he will come over and nip my hand and when I lift it up he puffs up his head and shoves it underneath my fingers because he wants a scratch.
He likes to burrow into clothing or other dark spaces. This is apparently a GCC thing because I've seen other people say on forums that their GCC likes to burrow into clothing. He drives me nuts because he's learned to flatten his body and squirm under the couch and I do what I can to prevent him from doing that but sometimes he gets away from me and disappears before I can grab him.
He never wants to go into his cage. My birds spend 10 - 12 hours per day out of their cage but he doesn't even want to be in his cage for 5 minutes. If it was up to him he'd never be in his cage. At night he knows it's bedtime and he gets very nippy with me because he knows it means he's going in his cage. He cuddles up to my husband's neck and falls asleep he wants to stay there!
He does a hilarious dance whenever he hears running water. He also does it if he hears music he likes or if people clap their hands. This is apparently a GCC thing because if you look on YouTube you can find videos of GCCs doing "the dance." Here's two videos I found:
Green cheek water danceGreen cheek danceThey are not loud birds generally speaking but they do have a "conure scream" that is pretty loud and abrasive to the ears. Mine only does it if he's scared or unhappy but sometimes he will just carry on with that call and it's tolerable but unpleasant to hear. Mine talks; he says about 10 different words and phrases and he uses them in context. His voice is rough (typical of a GCC) but you can understand what he's saying.
In summary they are high-energy, demanding, fearless birds full of attitude. They are also full of cuddles and love and affection and they do a hilarious dance. Their plumage is beautiful and full of colors and they have an adorable face.
I also have a brown-headed parrot (a Poi like a Senegal) so if you have questions about that I'd be happy to tell you about my other bird. He weighs in at 130 grams which is twice as much as my conure at 65 grams. Just so you are aware Pois have much larger beaks than GCCs and their bites are much worse. I'm not discouraging you from getting a Senegal but beak size may be a consideration.