I'll take a stab at it!
Of the 1st 12 images, starting from the bottom left (the masked guy), the bottom row is not 50mm 1.2. They don't scream "1.2" to me.
The next row, above, I'll say the tunnel woman is not, the horse nose is most certainly not, the purple shirted kid is.
The wheat field is not. The kid on the far right (with chin cut off) is not.
On the top row the umbrella girl *is* 50mm 1.2. The ants are not. The kid is not. The rose is (I'm not convinced 100%).
To recap I am saying the umbrella, the rose and the purple shirted kid are all 50mm 1.2 I was torn on the wheatfield I'll admit and not sold on the rose. However, when I viewed these images they are low res jpgs and rapidly pixellate on my monitor. The argument is "I should know immediately, it should be evident, if they are 1.2L" but my vision isn't the greatest and I use a 30" high end monitor and have to zoom in to see much of anything nowadays (sadly pixel peeping isn't intentional when one's eyes go bad, it is just a fact of life :-)). The low res of the images certainly isn't doing these eyes any favors but I do love the challenge!
After reading the entire thread, as a scientist, I'd predict I could tell the difference if the images were identical, as others have indicated. The (antag?)onist of the thread argues mixing images and lenses shouldn't matter, for if it has magical qualities they should be self-evident. I understand that logic but, with these samples, the low res jpg files prevented me from confidently (other than the umbrella girl and, in disagreement with a previous poster, the dog on the second set of 12) declaring 1.2 vs "other" in some cases.
As others before have argued the various 50mm lenses are different brushes that provide different results. I know my wife consistently picked the 200/2.0 images over my beloved 70-200 2.8 images. Is she 100% right on picking them out? Nope, but she picked enough out that, get this, she asked me to buy that awesome 200/2.0 lens!
I've owned the 1.2 and I own the 50 1.4. Is the 1.2 magical? For me it wasn't magical enough to keep (there were Great Whites to be purchased! :-)). Unlike the 200 2.0 and, to a lesser extent, the 85L, I personally wasn't able to consistently tell which 50mm lens generated an image and, more importantly, neither could the Big Boss (aka my spouse). I believe just about any lens can produce some amazing images but, ultimately, each lens is, as a previous poster mentioned, but a brush, a tool, that can do things other brushes can't.
I have enjoyed this thread, and the 24 image challenge. I ask that, at some point, we get to know which are the 1.2 images!
I love this forum. I learn so while mostly lurking, and the passion exuded by all parties is very cool and most appreciated.