They could well be Den. compactum x Den biggibum or something similar.
A hardware chain down here in Oz were selling the above as tiny plants. I bought one in November 2008 and it flowered for me this June and it is still a tiny plant.
Mine has pretty little (25-30mm) mauve flowers of the biggibum shape.
I have another similar plant with bigibbum and fantasyland in it's family.