In December of 2005, Batman's arch-foe The Penguin was inducted into the TV Crossover Hall Of Fame, having met the minimum requirement of three separate appearances:
1] 'Batman' - the series
2] 'Batman' - the 1966 movie
(This film has been "officially" absorbed out of the Cineverse and into the TV Universe.)
3] A cameo in 'The Monkees'
It could be that The Penguin may get inducted into the TVXOHOF again, because of his Toonverse doppelganger. Already the villain was seen in 'The New Adventures Of Batman' and in a guest appearance in "The Dynamic Scooby-Doo Affair", a Scooby-Doo "movie".
This past year, The Penguin showed up again - this time as one of Wayne's foes in a flashback on 'The Simpsons'.