Volume 1 of the manga series The Different Story tells a story about Mami and Kyouko before the timeframe of the anime series, when they were partners and Kyouko regarded Mami as a big sister.
(Makes me wish KyoMami was a more popular pairing.)
From the events of Volumes 2 and 3, we can infer that The Different Story is one of the hundred or so timelines that Homura experienced as she was trying to fulfil Madoka's last request, as seen in Episode 10 of the series. But the events of Volume 1 take place before Homura started going back in time. Does that mean that this partnership between Kyouko and Mami happened in every timeline, including the main anime timeline that ends with Madoka becoming Ultimate Madoka?