Factual error: In 1999 when April is filming inside the research facility, you can see her video camera displaying Bluetooth, which wasn't available in cameras until 2002.
Factual error: After the sewer invasion, April watches the three captured turtles drive away, then she turns to go to Splinter. Shortly thereafter, the computer screen shows GPS tracking the turtles at a location easily over an hour away from Manhattan. Likewise, the estate is referred to as being just forty minutes away from the city. (00:56:10 - 00:58:50)
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.
Sierra1 ★