Old Who Invasion by NuWho Monsters.

So which NuWho monsters do you think would have worked in classic Who?

Which era would they suit best?

And how would they need to be adapted to fit said eras, and the production style, budget and types of storytelling of the time?

Blink is probably the only New Who episode I can imagine being done in Classic Who.

So the Weeping Angels (though I think they'd only make sense in either Season 16 or 25-26).