Throughout his several weeks of unconsciousness, Avatar Aang had countless dreams, from odd ones to downright scary ones, but he didn't remember a single one when he woke up.
He met with his past incarnations to talk about his failure, which was only a weird thing to dream about because seeing those faces—empathic Roku, impatient Kyoshi, lamenting Kuruk, and wise Yangchen—had felt so real.
Then there was one where Guru Pathik rewired his back with onion-banana juice, making him invulnerable to both Earthly attachments and fiery attacks. The Aang in the dream put up no fight, and his Sokka declared the plan genius.
Once, Azula captured Aang and handed him over to her odd, perky friend—Ty Lee, was it?—who tried to turn him into her old circus' new star. He was helplessly trapped in the middle of a flaming hoop. Appa got him out of that mess, and Toph remarked that even that furball would make a better Avatar than him.
One of the worst began with another Spirit World journey. Katara tagged along because she suddenly wanted to find Jet, which was bad enough already, but then she took a wrong turn. She wound up in Koh's lair. Aang screamed at her to get out while she still could, and she yelled back that he should stop pathetically trying to hold on to her. Koh had her within seconds.
Ironically, it was Katara who comforted him throughout these deadly dreams of lies. She didn't know what was happening, and he was in too deep to even feel her presence, but she sat by him anyway, for she felt a sense of attachment she didn't want to decode.