That,That is,is,That,That is not,is not

Can anybody help me I've been trying to find the ending for this phrase for a while. I first saw the phrase in a movie just like the "Lawn Mower Man" but much older when a simple man is turned into a genius.

Just in case you didn't read the subject line
the beginning of the phrase is.
That,That is,is,That,That is not,is not

Don't recognize the quote, but could the movie in question be "Charly"? It starred cliff robertson, based on the novel "Flowers for Algernon," about a simpleton turned into a genius. As I remember, a well-crafted tearjerker flick.