Teenage Mutant Ninja Turtles

Question: How does Splinter know who shredder is? It's established that his first memories are from the lab so that's how he knows Eric Sacks is a bad guy and April saved them, but how does Splinter know Sacks is working for the foot and is connected to shredder? He even knows shredder trained Sacks as a boy, but this was in Japan, 20 to 30 years before Splinter was around.

Chosen answer: Sacks told April that he was raised in Japan by a local sensei, and that he shared the lessons he learnt with her father. Splinter would have overheard Sacks mention his master at the lab, as well as when O'Neil discovered what he was up to with Project Renaissance and his connection to Shredder and the Foot Clan.