[fenomas]

None in that case. I don't know of any general rules for when particles can be dropped, but sitting here thinking of examples, it's usually done for simple, direct sentences where the particle would be tying together two words whose relationship is already obvious:

> eiga miru?

> ano hon, suki?

> ame futte kita.

> okaasan iru?

And so on. But I don't think that's a rule you can work backwards from, it just describes all the cases that occur to me.