definitely not "intelligent and appropriately serious in demeanor". It makes me wonder if whoever wrote that actually saw the show or read the comics. She is nice, caring person but she is also a superficial, over-romantic, fun-loving, whiny and scatter-brained child, immature even for a girl in her lower teens. She readily admits it herself. Perhaps whoever wrote this was thinking of Sailor Venus who is also blonde and fits the description much better. Usagi Tsukino actually fits the dumb blonde cliché much better than the description above.