The bonus stage can be accessed by collecting 50 or more bones. In this bonus stage you play as Dogmatix, Obelix's dog. He takes no damage but can still be stunned by spikes. The selector cycles around like a slot machine, and when you push a button it slows down and finally chooses a difficulty. The difficulty determines the frequency of spike pits (Easy has none) and the difficulty of the bubble layouts. The objective is to pop as many bubbles as possible. You achieve this by bouncing on them. Green changes to yellow, and then to red, and when a red balloon is stepped on it pops shortly after.
You earn 1000 points for a green bubble, 500 for yellow, and 100 for red. These values are the same across all three difficulty levels.