Helvetica and Didot.

I think Jan has probably answered the font question. As for other pairings, I think the goal would be to (probably) find similar weights, but dissimilar styles. So this means, for example, don't use a mix from a superfamily that has both serif and sans versions of the same font.

Maybe experiment with varying the weights too, now that I think of it. Might be more interesting than keeping the same weights. Anyway, I think it's been done many times, but it can be fun mixing unexpected combinations.

- Mike Yanega

Thank you so much, Jan! Right after I posted I realized the reason the first looked so familiary was that it was Helvetica, but I never would have recognized Didot.

And thank you, Mike, for the advice. I am going to start experimenting right now!

Just for fun, here are some mixes using fonts I had active at the time. I tried to contrast the weight and vintage of the fonts.

- Mike Yanega

Also, look for similar skeleton structures! Are the round shapes oval, or circular? How open are the counters? How high does the n curve start on the left stem? Is the x height vs cap height similar enough? Similarities in width proportions. All of these does not have to match, but they must harmonize somehow.

modernfamily feels much like an homage to Vignelli's Bodoni/Helvetica juxtapositions for IDCNY (down to the warm red).
Of more recent vintage, the "holdeverything" logo attempted a Helvetica/Bodoni combo, but the x heights were not as well matched.

Happy hunting!

Walbaum/Helvetica is a nice combo.

- Lex