I bought one for $1.99.
Overall, Burger King's Whopper Dog turned out better than I expected and did indeed feel like a cross between a hot dog and a Whopper. It's worth a try if you're the curious sort. That being said, it was just okay as a hot dog.
Nutritional Info - Burger King Whopper Dog
Calories - 380 (from Fat - 220)
Fat - 24g (Saturated Fat - 8g)
Sodium - 1040mg
Carbs - 30g (Sugar - 8g)
Protein - 11