definitely its possible to have a "multi sire" litter, which would account for the disparate size and appearance between dandy and the single female compared to the other puppies. he looks very flat coated retriever to me, but i know the parents and while dad is big, they are no doubt border collies. well, he got the important part, so that's all that matters lol.
oh, interesting thing: i only just found out about a week ago that he's got brown right around his bottom lip! i don't know if it was there and i never noticed or if it's only just developed, but he's got the thinnest brown strip (about a 1/2") on either side of his bottom lip and he's developing a white 'stache. i guess technically, that would make him a tricolour, eh?
mum: black and white border collie, weighed 27lbs at the time (she was *teeny* and so were all the other pups - the ones that survived, that is). she was the kind looked like a fox - smooth coat with pronounced feathers.
dad: black and white border collie, weighed 60lbs - the kind with a thick, upstanding coat and looking rather like a panda bear. almost a dead ringer for the father dog in "babe". this dog is extremely similar (just turn the brown black and make the white strip even narrower up the nose, almost disappearing between the ears):
http://www.risingsunfarm.com/photos/spot/Spot-facelg.jpg
this dog is a cross betw a flat-coated retriever and a border collie:
http://farm3.static.flickr.com/2186/2009230076_610784033a.jpg
had ppl on at me to do a DNA test but i think that would suck all the fun out of it.