and another 500 years of fighting begins

There's another joke here, could be.

In the bleach series, there is a fact that the most commonly used phrase in the whole manga / anime is the phrase 'What.. did you say!?', which is what Remilia is saying right now.

So it may be referring to it.

I doubt it's a reference. That particular phrase is common not only in Bleach but throughout all manga/anime.

Someone got into Sakuyas pads it seems...-knifed-