Aug. 14 (UPI) -- Sylvester Stallone started filming his This is Us Season 2 guest spot over the weekend.
"On the THIS IS US set with Justin Hartley, this is a fantastic show and he is great to work with! #thisisus @justinhartley," Stallone captioned a picture on Instagram with Hartley.
"My good buddy Milo Ventimiglia who was nice enough to invite me to be on the show #thisisus #harleydavidson," he added to a snapshot with Ventimiglia.
Stallone previously worked with Ventimiglia on the 2006 movie Rocky Balboa. Ventimiglia told Entertainment Tonight this month he's "thrilled" to reunite with Stallone on This is Us.
"It's nice to know that the material attracts the greats even like Sly," the 40-year-old actor said. "And to know that he'd want to be a part and play with us, it's a very good feeling, so we're thrilled."
This is Us also stars Mandy Moore, Sterling K. Brown and Chris Sullivan. Executive producer Dan Fogelman said at the Television Critics Association summer press tour this month that Stallone will play Kevin's co-star.
"Kevin is shooting a big movie and we needed his big co-star, and Sly Stallone is coming to do a huge part on the show as Kevin's co-star and father figure in the film he's shooting," Fogelman shared, according to Us Weekly.
"We have a great script for him," he added. "I think it's going to be really, really exciting."
This is Us Season 2 will premiere Sept. 26.