There are about five people in the world who will get this, but:
Somebody* vs Casanova Frankenstein and Tony P and his Disco Boys (from the Mystery Men movie). They’re finally defeated and it turns out they were the mentors of Tigerlily Jones (from Skinhorse), who unleashes the power of funk in the form of a giant mecha.
Tip, Unity, and Sweetheart have to show up. Preferably Zeta and Foot wander through.
Like I said, I can’t write it. I’m not awesome enough. If you write it and it’s fabulous, I would honestly marry you. Not even kidding.
* I was originally thinking Cumberbatch!Sherlock, but on further thought there’s probably too much of a tone mismatch there. I think it would be better if whoever it was more low-key (so not, like, the Gurren Lagann crew… or even Sailor Moon). Batman could be great. Superman would probably be better. But somebody minimally powered – where they’re using their brain and not superpowers, would be so sweet.
On the other hand, the Creeper or Freakazoid could be really awesome.