I guess I am missing something here, who is this Miiko-character the sisters are talking?

Deathmatcher said:
I guess I am missing something here, who is this Miiko-character the sisters are talking?

A google search didn't reveal much in particular about the name Miiko, except　that it seems to be a common name for a cat.
The shadowy figure in panel 4 looks a little like Doraemon, a mechanical cat who came from the future, it could be a reference to that (he doesn't have ears either, they were eaten by robotic mice.)

bordkarton said:

I see, well, that actually makes sense if you think about it. There certainly is some kind of wordplay with Miko and Miiko there.

But a shadowly head in Koishi's speech in panel 4 looks a lot like Mickey, so maybe there is two references at one time?