A mutation?
 

I bought a Wilson Hilda plumtree from an orchid show and all the buds have been opening. And then, this one caught my eye. Two flowers in one? Has anyone else experienced this? Hopefully this is a good picture to see it.

Looks like something could have happened while the bud was forming and caused the cells to partially split, like conjoined twins?

As they say ... "Sh..happens". Nothing to e concerned about, and likely nothing you'll ever see again on that plant.

Sometimes flowers fail to develop properly. Sometimes mericlones do pick up mutations in the flask from the growth regulators added. It will be interesting to see whether your plant does this in the future; it probably will not, but there is a slim chance it will do it again.