Teenage Mutant Ninja Turtles S02E02 - The Incredible Shrinking Turtles

The turtles seek out the fragments of the eye of Sarnoth, a crystal with unimaginable power. After finding the first fragment, Shredder steals it and uses it to shrink the turtles. Now Splinter and April must intervene. April is able to enlarge the Turtles, but our heroes lose in the end as Shredder escapes with the first fragment.