"A" was teasing "a" about how clean his bedroom was and how he just might move home and take over the nice bedroom... and "a" could sleep outside.
"a" was having none of it. He wanted a sign on his door... only he doesn't know how to spell. So he asked "A" to help him. "A" was a good big brother and helped his kid brother spell out the following:
no "A" allowed
this is "a"s bedroom