Thomas Ian Griffith is actually 4 months younger than Ralph Macchio, but plays a character believed to be significantly older than LaRusso.
Thomas Ian Griffith studied Tae Kwon Do since childhood. He's also a black belt in Kenpo Karate, he's trained in kickboxing, wrestling, and fencing and has experience in stage combat.
This marks Thomas Ian Griffith's first acting role in 14 years, since the 2007 TV movie The Kidnapping (2007).
The crew responded to the passing of Ed Asner by saying what little time they got to spend with him in what ended up being his final acting role was always a joy, and he was constantly cracking them up right to the end.
The bottle of wine Terry kicks right before the credits is a bottle of Kamen "Lava Block", which is actually produced by Robert Mark Kamen, writer of the original trilogy.