In creative mode, powder snow is able to be made into a ghost block.

Steps to reproduce:

1. Be in creative mode.
2. Replace a block in the ground with powder snow.
3. Stand so you're touching the space of the block above the powder snow.
4. Place a bucket of lava on top of the powder snow, and quickly place a bucket of powder snow inside the lava.
5. Visually, the newly placed powder snow breaks. However, it often stays as a ghost block. This can be shown by the block space giving entities the freezing effect, or by trying to place a block where it was, and the block then turning into powder snow.