4yo DS had a meltdown the afternoon of Easter Sunday, after lunch at home, suuuuper tired (naps at school but won't at home) and high on candy. He was mad because I wouldn't let him have more candy, which is a pretty typical REASON for a meltdown, but he was so deliriously tired he was convinced he was at school and we were refusing to take him home (to eat more candy). I got it on video.
He also used to have a meltdown if I gave him a granola bar and it broke in half -- he tried to insist that he could only eat the whole ones.