Shouldn't be any reason it's not possible. The Mac Mini uses (I think) a Socket M, so anything that'll fit that socket should work... Physically, anyway. Dunno if the chipset on the MM logic board will play nice with Penryn. One way to find out I guess.
I think you will find a problem with that...I would have to check with one of my sources but on previous versions of the mini, the CPU was soldered to the mainboard and couldn't be replaced
^^ correct i recall, on the mini and most all their laptops, it is soldered in, many claim reason for stability, in laptops, to take up less room, but for me is it simple a way for Apple to force you to buy new systems intead of upgrading current ones
Socket physical fit wise, yes most likely as long as it is an intel based one. But actually working is another story..the chipset nad board has to support the new processor which is not gauranteed even if it fits...