There is an episode in Ranma 1/2 where Shampoo demonstrates
an instant 'jusenkyou' cure and drops a dog into a water-filled
drum, turning the dog into a boy that looks remarkably like Ataru
from Urusei Yatsura.
Theres also another episode (cant remember for the life of me
which one) that I watched a few weeks ago where Kasumi
is doing her shopping and in one of the nearby stalls you see Kyoko walking
by w/ groceries.