This is the second time a Five Nights at Freddy's entry has ever featured a YouTuber in a trailer, which is Markiplier in this case. The first was Ultimate Custom Night, with Razzbowski, Dawko, FusionZGamer, 8-BitRyan, and CoryxKenshin's gameplay video featuring in the trailer.
The YouTuber Markiplier starred in the game's launch trailer as a spokesperson of Fazbear Funtime Service. It is currently unknown, including to Markiplier himself, if his inclusion in the trailer is considered canon as part of the series.
This is the third game in the franchise that is free-to-play, following Freddy Fazbear's Pizzeria Simulator, and Ultimate Custom Night.
In Dawko's interview with Scott Cawthon, he mentioned that he planned to have an augmented reality game some day, with that being Special Delivery.
Illumix had revealed multiple characters who are confirmed/planned to arrive to the game in the future. These are animatronics that were discovered in the files for the game, that were mentioned in interviews, or were secretly teased in promotional material.