Far as I know, Happy Feet wasn't a spoof of Pebble and the Penguin.
Actually if you compare several plot-points in the movies, they appear to be very similar.
Hubie = Mumble, they are both shy at first and both a have a love interest
Marina = Gloria, they both are both beautiful penguins, they are both good singers and they both have a shy love interest.
HubiexMarina = MumblexGloria = They are both seperated from each other for most of the movies.
Mumble and Hubie are both chased by a leopard seal and killer whales.
Both Mumble and Hubie are captured by humans to be taken to a zoo
Both movies are comedy romance and musicials
Neither Mumble nor Hubie can sing
The endings are very similar too, both Main characters get girls in the end and have a child(ren)
The endings both left an opening for a sequel (Happy Feet : Yes

, Pebble : No

)
They both begin with all the penguins singing and dancing, just the orders are reversed in Happy Feet it was girls first, in pebble it was the boys first
Both movies feature singing and dancing penguins