The unused villains are Sinestro, Toyman, Black Manta, Captain Cold, and Braniac.
The Legion of Doom send overly cute gigantic animals to disrupt the governments of the world!
First, a dog at Washington DC! Once that's resolved, there are animals in all the major capital cities of the world! A fluffy white cat at London, a hamster at Moscow, a rattlesnake at the Great Wall of China, and a kangaroo at Sydney!
Why? So the Legion of Doom can steal government records on research into animal intelligence!
Why? So the Legion of Doom can create super-intelligent animals to defeat the Super Friends!
How? By collecting the mightiest animals of all time and giving them super-intelligence!
Who? King Kong, Tyrannosaurus Rex, Shere Khan, and Moby Dick!
How? By travelling through time!
Why? Because this plan cannot possibly fail!
Some sample "Super-Riddles" for the Riddler to use!