Space Squad is the movie said Kyuranger episode was advertising.

And honestly I'd probably go as far as to call it my favourite toku crossover ever. Especially if they deliver on that ending and do another one.

Did you see it in Japan? Wasn't it a theatrical movie?

Yeah, but that flick has been subbed quite some time ago by Over-Time. Same with Episode 0, its prequel.
Btw, how much knowledge about Dekaranger and Space Sherrifs should I have before watching that flick? So far I've only seen the original Gavan show.

While I haven't seen it yet, the Kyuranger episode suggested it having quite a few inside jokes from Dekaranger, so I'd recommend watching it first tbh.
It would certainly also help to at least have seen the first of the Next Generation Space Sheriff movies, because the guys in those movies are the faces of the Gavan half of that one.

I think to get the most out of the movie it's best if you've seen Dekaranger, Gavan, and Juspion.

It was theatrical for about a month and then the BD/DVD came out immediately after.

Dekaranger definitely, as well as 10 Years After.
Gavan you only need to have really seen the movie and then the Next Gen Space Sheriff movies.
Juspion....eh. You might get a little more out of it (mainly a bit more context on Mad Gallant and Satan Goth) but its not essential.

Having seen all of Juspion, I can confirm it's not necessary. There's some cute references but that's about it.

Honestly given Satan Goth's depiction, I'm not even sure the writer(s) have seen Juspion. Because Goth isn't mechanical.

Hah, I haven't even seen Juspion and I wondered what was up with that :lol

It's a fun series and I recommend it. It has some short comings and I do think there are other series worth watching before hand. But I still enjoyed my time with it.

Yeah the depiction was bizarre. I guess they didn't want the whole mask since it would look like a lawsuit from Disney waiting to happen. But they had other ways around that.

I think they were stuck between that and choosing a form that folks would recognize instantly as being Satan Goth.

It didn't work out all that well, that much I can agree on.