Same happened to me! you can see the conversation here w the explanation: http://forums.gardenweb.com/discussions/3159852/garlic-behaving-strangely?n=6

i saved the big bulbils to plant this fall.

This is the second year in a row my Japanese garlic has done this. Bulb size is still reasonable, and with its reduced numbers of cloves they are large enough sized to be really handy. None of my other garlics do this, although I have noticed that some of the softnecks in the grocery store set what looks like a bulbil just above the actual bulb and so deep inside the neck that it never gets exposed. I also grew some true softnecks this year and none of them did this either; for me this is just on the Japanese. I will also have a nice set of large Japanese bulbils to set out this fall.