clefable and blissey can be found by a trainer on Route 210 west of the house.
no only by breeding wobbufet
Sorry, you can not get tepig in pokemon diamond version because diamond is a 4th generation game and tepig is a 5th generation pokemon. Get black/white!
If you haven't encountered it then there is a possibility that it might not have a Trainer with a Rufflet. This fact might support the question: "Rufflet is exclusive to Pokemon White Version. And Vullaby is exclusive to Pokemon Black Version."
By trading one from gold/silver and cloning it Dani (the girl Pokemon trainer on Pokemon crystal version) By trading one from gold/silver and cloning it Dani (the girl Pokemon trainer on Pokemon crystal version)
The site listed below has a chart for the Pokemon Finneon Diamond and Pearl edition.