"Unyu?" (うにゅ?) has become her trademark sound, ever since she said it in the Extra Stage back story.
Because Utsuho is manipulated by Kanako, seems to have a simple and boastful personality, and is called a birdbrain by Orin, she's often considered an idiot by fans. ZUN also indirectly calls her an idiot in her theme song's description. This leads to comparisons (or pairings) with Cirno, and as the stage 6 boss, Utsuho is sometimes called ⑥ (which is an inverted ⑨).
Even when Okuu is quite manipulated by the Yatagarasu, she still has basic knowledge. She doesn't really know much about anything (or at least her knowledge about everything else is average) except for nuclear physics. She's a mastermind every time it comes to Physics. If Okuu doesn't understand the current topic of conversation, she gets confused and immediately tries to change the topic. She is a savant. She learned from anything she heard. That means she maybe can be only a bit stupid, but she isn't a complete moron as everyone thinks she is.
Her arm cannon in UNL has led to fans parodying the Mega Man games with her. She's also shown in one fan work to have a crush on Bass.