(Maybe another hint that Rebels will serve as connective tissue for Mandalorian's universe.) It has appeared in Star Wars comic books and novels in recent years, and it has shown up in animated form plenty of times in Disney's Star Wars Rebels, as well as in the corresponding Rebels tie-in lore. On the contrary, the transporter has popped up in many different project, both canonical and non-canonical.
Now, just because The Mandalorian is the first live-action project to include the Imperial Troop Transport, that doesn't mean the vehicle has only existed in toy form over the past four decades. And considering kids at the time probably didn't have a half-dozen spare Stormtrooper toys, I assume kids transported many different franchises' main characters between fictional locations. Naturally, the toy itself didn't come filled with Stormtroopers, which were sold separately. The Imperial Troop Transport featured six buttons that activated quotes and sound effects from the Star Wars film, such as cannons, with R2D2 and C-3PO also thrown into the mix.
