There have been no episode where all of them have gathered in a single episode, but they each made individual reappearance in later episodes.
Misty reappered in "The Princess and the Togepi" (AG044) and "A Togepi Mirage!" (AG044) where May also starred.
May reappered in "Our Cup Runneth Over!" (DP075) to "Strategy With a Smile!" (DP079) where Dawn also starred.
Dawn appered in "Piplup, Pansage, and a Meeting of the Times!" (BW086) with Iris.
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