I have a rat terrier male and i was wondering if its possible to breed him with something the size of a lab. Would the puppies be healthy? Would they physically be able to mate?

you could, but please dont. The female would have to be laying down and you would most likely have to "help" the male to be able to get in there and do his business. But really this whole "designer breed" thing is getting out of control. Not to mention that breeeding just adds to the overpopulation and eventual destruction of the animals in shelters.

are you crazy???? why would you want to? it would be an experiment, an unsafe, unethical, immoral, harmful to the animals, useless thing to do! please do not make the dogs GO THROUGH THAT TORTURE just so you can see if the puppies might be cute or worth selling. please have your dog neutered...there are already so many dogs that they have to be KILLED b/c people won't stop breeding them and saving the ones that are already here and needing homes! come on! think about it! say you made 5 puppies and all your friends took one. well 5 other puppies just had to be killed b/c no one came to the shelter to look at them. they were already there waiting! if you do this you are contributing to the problem.