Hikaru's "Twincool".
I've said it before, but I'll say it here, I don't have a problem with character having a catchphrase.
There's plenty of characters from Toku, anime, or a lot of media in general that I like with catchphrases. But with Hikaru in particular is the same issue I have with Takaharu's and Lucky's, she'll just say it for no reason at the most random circumstances when they're not needed, and its her only character trait.

I don't like Hikaru in general as a character, and this is one of the reasons why.