Japanese Language Question: ??????

OK, “Soramimi Cake?”

I come up with “Cake of Mishearing” or “Fancy Hearing Cake,” but, in English, that is a nonsense phrase.

I think I need a native (or near native speaker) on this one. Is this idiomatic, or a cultural “in” joke, or what?

This is the title of the opening theme for the anime “Azumanga Daioh,” which, BTW…is also a nonsense phrase.

Anyway, I have checked all of the obvious places, including anime blogs, language blogs, and even Wiki.

Help please?
Great site…thanks.

BTW, I have an Apple Poster on my wall, with the other five girls in Black&White, Osaka in color…with her usual spacey look. The caption says, “Think Different.”

I pride myself on being the World’s Oldest Otaku. In addition to my boxed anime and Japanese cinema, I have over 5Tb of fansubs, unlicensed (in USA), and out of print film & anime. …and then there are the figures…LOL

I am probably the first person in the history of the Universe to be learning Japanese because he hates dubbed cinema and anime.
BTW, haven’t read the manga you posted yet. My reading skills aren’t up to par with my substandard spoken Japanese. :-)
Naruto is a truly awful dub…but the unabashed KING of bad dubs is the hideous dub of Ah! Megamisama! How anybody can listen to that awful voice acting is beyond me. You lose SO much in English dubs. In fact, the only decent English dubs are Azumanga Daioh and Evangelion…all of the rest are just awful, except maybe Shinchan. LOL