Improbable Island has many races, each with it's own unique attributes. Below is a list of Races that have been spotted on the Island. Some of these races are better documented than others, as some are quite rare. Due to rampant Improbability on the Island, several unique creatures exist. Please note that the definition of races do not include these evolutionary failures, unless there is a sufficiently large enough gene pool to guarantee continued survival of the species.
These contestants have been so infused with Improbability, even their narrators have become infected.
An approximation to the bonuses and penalties each race has can be found in this link.
Or, as a Rookie helpfully summarised it for all those to lazy to study further : "Zobbies got Om Nom, Mutants have Rawr, Robots have Beep-Boop, Squats have Impotent Rage, Jokers have WTF, Humans have boringness and Kittehs have Floof and Claws."