I walked into Toys R Us yesterday to scan the shelves & found Black Adam & Captain Marvel in a box that said "Mad Love" & it appears Harley Quinn & Joker are supposed to reside therein. Looks like BA & Cap should be in the "Mightiest Mortals" package. DC Universe Classics, of course, 6" line. Should I snap that up because it will be worth something or ignore it? Don't know how much interest there is in factory mistakes like that.

Thank you, sirs.

That's not a factory mistake. That's a cheap skate who returned the package with the wrong figures in it.

Ignore it.

Or better yet, bring it to the attention of the store's Loss Prevention person and let them know they were taken advantage of and that they now have defective product on the shelf.

Unless you know someone who is a "mistake" collector, it just isn't worth the effort. Very, VERY FEW people care enough about a "packaging error" to give it any value.

10-4, guys, I appreciate you weighing in on this so quickly! Many blessings.

I'd say that it's more likely an error from the factory. Both sets were in production at the same time and it's not unknown for something to slip out in the wrong packaging. If it had been, say, Aquaman and Black Manta in the box it would be far more likely to have been a figure-swap.

That said, I still wouldn't recommend it for an attempted re-sell. Very limited collectors market for mis-packages and would be a much easier sell if it had been Joker and Harley in the wrong box than Cap and Adam.