The same way people fart is how a rabbit farts! In fact, nearly all animals do, as it's a necessary part of digesting food.
Fart lighting, pyroflatulence or flatus ignition is the practice of igniting the gases produced by human flatulence, often producing a flame of a blue hue, hence the act being known colloquially as a "blue angel", "blue dart", or in Australia, a "blue flame". The fact that flatus is flammable, and the actual combustion of it through this practice, gives rise to much humourous derivation. Other colors of flame such as orange and yellow are possible with the color dependent on the mixture of gases formed in the colon.
Although there is little scientific discourse on the combustive properties of flatus, there are many anecdotal accounts of flatus ignition and the activity has increasingly found its way into popular culture with references in comic routines, movies, and television; including cartoons.
Flatulence humor refers to any type of joke, practical joke device, or other off-color humor related to flatulence.