Explanations

The ninas are: STRINGS, STINKS.

At the top-left and the bottom-right, there are two 4×4 “15 Puzzles.” The letters in the first 15 Puzzle can be scrambled (as indicated by “Break”) to “Rogue PUPPETEERS.” The letters in the second 15 Puzzle can be scrambled (as indicated by “Concoction”) to “Nose At War: EGGNOG.” Filling the ninas in completes the two wacky headlines:

Rogue Puppeteers Break Strings
Nose At War: Eggnog Concoction Stinks

Notes

I think the “endgame” in this puzzle is quite simple if the solver is familiar with what a “15 puzzle” is. Here’s the Wikipedia link: en.wikipedia.org/wiki/15_puzzle . Perhaps most folks have actually played with a 15 puzzle, but some may not be familiar with its name. As an aside, the 15 puzzle is usually solved in raster order (left-to-right and top-to-bottom), but there is another way that is mathematically cute: get the top row and the left column right, and now you have reduced the 4×4 puzzle to a 3×3 puzzle. Repeat the same reduction strategy!