In the anime, Prairie-chan greeted Bag-chan, Serval-chan, and Beaver-dono with a big kiss on the lips. It left both Serval-chan and Bag-chan quite flustered. (Presumably it had the same effect on Beaver-dono, but we didn't actually see it on screen.)
In this comic, Bag-chan turns the tables, presumably by being a lot better at kissing than Prairie-chan. I suspect some tongue was involved.