The Legendary Dogs (also called Legendary Beasts, Legendary Cats, and even, usually humorously, Legendary Gerbils) were available for the week of 25/7 to coincide with the release of version 3.3. There was a contest that the first ten people to beat the Vermillion Gym could keep one of the trio. There was one Mystery Gift code hunt for each of the beasts, Raikou , Entei , and Suicune. The three Pokemon have incredible base stats, each with a total of 580, stronger than any other Pokemon (excluding Mew, Dragonite, Mewtwo and Victini) programmed into the game thus far. They were only available for a week and then will be automatically removed from each player's profile. When they were Mystery Gift codes, Raikou knew Thunder and Thunder Wave, Entei knew Fire Blast and Fire Fang, and Suicune knew Blizzard and Hydro Pump.On Sam's blog he stated that he will make the Legendary Beasts appear with a chance lower than shiny Pokemon (< 0.1%; the exact percentage hasn't been released to prevent hacking). On his twitter, he stated that we can capture them without having to lower their health, like a Shiny Pokemon. With the release of version 5.1, the legendary beasts can learn moves by level up.
However, as the game became finalized, the legendary dogs were removed from the wild (v0.8) and all previously-obtained legendary dogs were changed to their shiny forms.
In ptd 2, as of 6-7-14, you can Buy them for 20 snd coins, or 2000 Daily Coins.