I have a distinct feeling that my goldies are upto something in one of my ponds.

I woke up this morning and when I looked out noticed that the top pond was a hive of activity with most of the goldfish I have in there chasing each other around. I threw some food in and although most came to the top to feed a few ignored it completely and just carried on. As such I have a number of questions that probably need answering (and it's not about the birds and the bees!!)
1) Do goldfish species cross breed i.e. will a normal (orange) goldfish and a comet be compatable? The reason I ask is that the cheif culprits were of the above types.
2) In light of the activity am I best leaving a small amount of Blanket Weed I have in there for the time being as I am led to believe that this is a good area for laying eggs in?
3) Should the miracle of miracles happen and I do get some fry, am I best taking them out and putting them in a tank?
4) I was always of the notion that Goldfish had to be of a certain size to breed i.e. quite big, Is this true? The one that looks like it is getting most of the "action" is about 4" long without tail - Would she be mature enough to spawn?
5) How common is it for pond fish to breed? I was always of the opinion that it would be quite rare. - Am I just being naive? How many other ppl who come on here have successfully bred fish?
6) Is there anything else specifically I need to do e.g. Feeding etc.
Thanks
Tony (i'm so proud)
