Why does Blender make bubbles? It's not that important for me now, but I'm curious: I was learning gradient shading and played around a little. I seperated a face from the mesh, made it a new object and then reconnected them... And Blender made bubbles... Any idea, what Blender wants to tell me? Neither have I applied particles anywhere in the file (even when the modifier is shown) nor have I included anything else that is not about the cube and its shading. The bubbles occured after the separation and some of them stayed after reconnecting.
Here's the file to see it yourself:
There is in fact a particle system on that cube, just delete it with the minus button.