Greg Nicotero has explained that this episode includes footage from the original pilot. At the end of the scene where Rick is in Atlanta, the camera hadn't been turned off until eight seconds after the direct called "cut." Digital effects then inserted Andrew Lincoln coming around the bus.
The Winnebago Jadis/Anne is seen in is the same one that went missing, with Heath, in season 7 when he and Tara went on the supply run that lead Tara to Oceanside. Jadis may have something to do with Heath's disappearance since she acquired his trailer. It's possible Jadis abducted him to be traded to the helicopter group.
Sadly, actor Scott Wilson, who portrayed the character of Hershel Greene, passed away shortly before the season 9 premiere, making him unable to appear again in the TWD universe unless archive footage or outtakes are used.
The crowbar Maggie (Lauren Cohan) takes with her when confronting Negan (Jeffrey Dean Morgan) was built to be the same size as Lucille.
This is the second time Wang Chung's Space Junk has been used in the series. It was also used during the closing credits of the pilot episode.