Generally speaking, being a serious athlete requires more muscle mass and substantially less body fat than the average person. Other than that, though, the overall size and how that mass is distributed can vary widely from person to person.
In most athletes, everything tends to come together pretty normally. You really don't find too many insane physical features among tennis players, soccer players or hockey players. They just don't lend themselves to freaky features.
But then there are some who look like they were Frankensteined together with spare monster parts—not that there's anything wrong with that. Let's take a look at a few such athletes.