Getting a song stuck in your head (commonly called "earworm", but I think that's a terrible name for it. I think "memelody" makes more sense) when you hear the tune or someone says something that reminds you of it I think qualifies as a meme but not an idea, especially if there is some shared culture reference that makes multiple people think of the same tune from similar stimuli.
I see, thanks a lot for your reply.
I think certain kinds of celebrity gossip may qualify as memes also. I'm confident that gossip is definitely not "ideas".
Thank you again, I should check strong definition of "idea" in use but anyway I see the point there.