This IS Foster's related, but I didn't know where else to put this without reviving an old thread, so my apologies. I also didn't think it was necessary to make a new thread for it... Anyways, today I found out what (maybe) happened to Berry after Affair Weather Friends. Since Berry is my favorite character, it definitely made MY day.
Basically, I was browsing the Foster's wiki and clicked on a page to an article on a Foster's comic, which was also a crossover with the Powerpuff Girls and other CN shows I guess, called Powerpuff Girls Super Smash-Up, from 2015. I read on the page that Berry was in it, so I got excited and searched for the comic, finding a video with all the panels of the comic. In the video for the 4th issue of the comic, a few minutes in Berry can be seen among other friends at the house in one panel, meaning either the comic is non-canon (probably) or Berry escaped the rubber band ball and came back to Foster's sometime after Affair Weather Friends.
Anyways, just an interesting lil thing I found, this is my new headcanon, replacing my old headcanon that Berry died. Again, my apologies since this probably isn't the best place to post this.
(Big image so I left it as a link)
She's in the bottom right corner.