Jerashid appears once again, this time in the Edo period of Japan. And no, it's not a past version of him, as he's still wearing his wedding ring. Best not to question how and why he got there.
Also stuck in the Edo period with no way to get back, Yoko, J, and Gai wonder how they can send a message to their allies in the present. J has the idea of writing a message to them, but Yoko asks the obvious question: Who could they trust to hold onto such a message for over 250 years? Gai then gets an idea. Cut to the present time, and Shiba Kaoru personally delivers that very message to the Go-busters' HQ.
Early-Bird Cameo: Like its predecessors, this movie marks the debut of the next Sentai team, Zyuden Sentai Kyoryuger, where they take on Waredonaiyer and some Zangyack grunts. This is notable for being the first early-bird cameo to take place inside a warehouse, as the previous three all took place out in the open.
It's also the first where a member of the cameo team meets with the two starring teams, as Kyoryu Red meets his two predecessors before his team's cameo proper start (the other members were late).
Fake Defector: Marvelous reveals to the Busters that their method was dealing with Zangyack from the inside through a pretend surrender, attacking their allies secretly. By the time the movie had started, they were already found out.
Let's You and Him Fight: The Go-Busters fight the Gokaigers, who have seemingly joined forces with the new Zangyack.
Mythology Gag: the whole point of the mechas transforming into other mecha.
Gokai-Oh -> Daibouken: the Boukengers are the Gokaigers' predecessors as the anniversary team, and both series have an adventure theme.
Marvelous even imitates Akashi by snapping his fingers and saying Attack!
GoZyuJin -> DaiZyuZin: the Zyuranger Greater Power is one of the components of GoZyuJin.
A minor one but GoZyuJin becoming DaiZyuZin also made a reference to Power Rangers' very first Megazord, production wise, and all the mechas are all called MegaZords.
Go-Buster Ace -> Gekitouja, Flash King and Ryuuseioh: All the Mechs are fast and agile. Gekitouja is composed of wild felines (even with a red one to boot), while Ryuuseioh is a red mech with his own robot form like Ace.
Go-Buster Lioh -> GaoKing and Gao Kentaurus: Li-Oh and King have lion mechs as the central component of the combined mode plus Kentaurus was the final mech of the Gaorangers just like Li-Oh.
Trapped in the Past: When Enter finds the last of the Phantom Ranger Keys, they react violently and open up a time portal, sending the Gokaigers, Yoko, J, and Gorisaki into the past with no way to get back.