.
Donatello
Da Vinci
Monet
Rembrandt
Shredder
Splinter
Rat
Foot
Kevin Eastman
Peter Laird
Laurence Fishburne
Kevin Smith
Ancient Monsters
Giant Rats
Aliens
Evil Ninjas
Morgan Freeman
James Earl Jones
Laurence Fishburne
Samuel L. Jackson
Mayan
Roman
Greek
Aztec
Karai
Casey Jones
April
Leonardo
It wasn't explained how he knew, he just did.
He overheard them fighting.
There was a report on the news about them.
Leonardo told him of the fight, while seeking advice.