Aha ha ha ha! I found something on the internet!
Well, not what you were hoping, but- according to a few Gummi Bears fan sites, the episode is probably from the sixth (last) season, and is called 'Rocking Chair Bear'. Now I have to go search for that.
But yeah, I remember the show too, and I loved it. Aside from the remarkably solid plots, great characters, and rich story background, there were a helluva lot of magical transformations. Tiny ogres becoming giants, characters switching bodies, characters turning into copies of eachother, characters getting turned to statues. Not all my things, but still- the creators had that special perversion.
--- EDIT ---
Well, here's the intro:
Doesn't look too hopeful for episode clips.
--- 2nd Edit ---
Well, this is the best I can do:
Somebody made a music video for the character Sunni which seems to show a lot of footage from the epsiode in question, but without the context of the story the change isn't too noticeable. The song is appropriate, though.