"Good Grief" episode gag?
When George Sr. (Pop-Pop) is in Mexico and is walking through the streets with the sad "Charlie Brown" music playing, you can see something is written on the wall he walks past, like "P.P.5.P." or something like that. You can see it in this image:
http://25.media.tumblr.com/tumblr_m7y9iynrKM1qcm16uo2_500.jpg
Is this an in-joke I'm not getting? I'm on my fourth run-through of the show and there are jokes I'm just now getting (like "Seaward" meaning "C-word" when it's first referenced.) I know the episode is full of Charlie Brown references. Is that one of them?
OR WAS I JUST NOT SUPPOSED TO CARE HUHHHH???