"You've got to be out of your mind man," says Astin, who plays Sam in the franchise.
Gad replies with a very persuasive argument: "You fought off an army of Orcs multiple times ... wounded the demon spider Shelob, ran away from Gollum, all to destroy the most powerful ring in the world.
"How hard can a f***ing phone call to Elijah Wood be?"
via GIPHY
Like magic, Elijah Wood joins the call and Gad persuades him to take part in the cast reunion.
One by one, different cast members join the call - including Orlando Bloom.
Bloom, who is engaged to pop star Katy Perry jokes "Katy has to remind me to turn the Zoom off in bed."
But, there is one key member of the reunion missing as Gad makes his final case for the LOTR reunion - Gandalf, who was played by Sir Ian McKellen.
via GIPHY
"So do I," says McKellen as he joins the call, reciting one of Gandalf's famous lines.
"And so do all who live to see such times. But that is not for them to decide. All we have to decide is what to do with the time that is given us."
Fans expressed their excitement for the reunion on Twitter.
Gad has hinted LOTR enthusiasts can expect "many surprises".
According to a screenshot of the call posted to TheOneRing.net, the call will feature New Zealand director Sir Peter Jackson, who directed all three LOTR movies as well as The Hobbit Trilogy.
The reunion special premieres on Monday June 1, at 4am NZST on youtube.com/joshgad.