An amazingly simply solution!

This is what a corner in our downstairs bathroom looks like:

We searched for a replacement but the weird corner angle was nowhere to be found. So my next method of coping was pretty much just to ignore it. Fast forward several years.

While I had forgotten the whole thing, the cracked tile continued to bother my very crafty mom and she finally came up with a do-it-yourself solution to fix the problem. The first step was to remove all the old tile (without cracking the neighboring tiles...). We proceeded carefully with a chisel, a razor, and a flat-head screwdriver. After a few minutes of careful cracking, we got all the pieces out:

We chisel right to the trim, because the tiny sliver of tile on the right wasn't in great shape either.

Next (and this is the really genius part), we mixed Plaster of Paris to a thick but pliable consistency and I got to work as sculptor on this masterpiece you see below. It wasn't as hard as I thought it would be to  slap the plaster up and shape it more or less in the shape of the missing tile.

The instructions said it would only take 20-40 minutes to dry and could then be sanded, but I don't think they accounted for the amount we used. It definitely wasn't dry after an hour and was still cool and slightly pliable the next day. When I tried to sand it, the layer immediately under the surface was still damp. So I waited a week before attempting the next step.

After the week, I did my best to sand the "tile" smooth. I also used the screwdriver and razor to clean up the edges and recreate "grout lines" where the plaster got onto its neighboring tiles. After the lines looked straight and clean (and after wiping off the plaster dust), I got to work on the paint. Mom suggested spray paint because it is so opaque and durable, which seemed like a good idea. I didn't think we'd want to try anything like a washable acrylic.

I taped the edges but definitely didn't want to spray the paint on directly, so I sprayed into a cup and used a paint brush to apply. The first coat went well.

The second coat? Well, not so much. Here's a little reenactment of what happened:

--Put on gloves, pick up red cup, shake spray can and begin spraying into cup with my head turned away to minimize inhalation and fumes in my eyes. Glance down to see spray paint dripping everywhere onto the floor. SCREAM!!!! Keep screaming, mostly incoherently, but with words enough to summon D and get his help to put the cup into a trash bag. Start scrubbing the floor with the nearest rag in attempt to remove spray paint, to no avail. Imagine that instead of one missing wall tile I would have to retile our e entire floor, all the while continuing to scream and while running into the kitchen for additional cleaning supplies. Grab dobie pad and baking soda, then, in a moment of clarity, grab Magic Eraser (D is still frantically scrubbing with a rag). Scrub Magic Eraser on floor with near-supersonic speeds. Take deep breath and black starts to fade. After a little more elbow grease, the spray paint on the floor is totally "erased."--

Thank goodness for Mr. Clean. Also, apparently, spray paint eats through plastic cups...There's no picture of all this because of the panic that ensued. But after what was probably only 60 seconds of horror, we were back to where we were with one coat of paint and ready for second coat. With a new cup (two stacked together actually), I started on round two. Then I pulled off the painters tape, got out the screwdriver again to etch back in a smoother "grout" line" and here is the result:

I waited a few days and then decided to try and match the shine of the surrounding tile with this product, Triple Thick Gloss Glaze:

 Here's how it looked after a couple coats:

I think it's a better match glossy. The only problem is that now that it's reflective, you can tell that the surface isn't that smooth. See? Here's the wavy effect exaggerated by the camera flash:

But in the end, it was an incredibly cheap and effective solution to the ugly cracked corner. And even though it sounds like a long process, it really didn't take much time at all. t can't believe it took us two and a half years to figure it out.