Did Will Smith really drop his lines in this episode of fresh prince with his dad?

I found this clip on tumblr. It was accompanied with "i've seen this
floating around tumblr a lot. it was at the start of will's career.
when talking about his father, will dropped his lines and it all
became real. the hug at the end of the scene was unrehearsed and
feelings were raw and genuine."
I am pretty sure this isn't true, but I was just curious if anyone
could confirm or not.

I'm pretty sure it's not, especially since they say it was the start
of his career, and it was in episode 424..