There's only so much space on the baselines in basketball, so it's rare for any shot to come from behind the basket during a basketball game. If they do come from behind the basket, they usually result in an air ball that turns into an easy rebound for the opposing team.
But making the so-called circus shot does happen, and each level of basketball has its own set of rules to determine if the shot counts.
National Collegiate Athletic Association
The NCAA rule for shooting over the backboard states, "The ball shall be out-of-bounds when any part of the ball passes over the backboard from any direction." This means a college basketball player can't score on such a shot even if the ball makes contact with the basket support or the back of the backboard. If it does, it's an automatic turnover.
National Basketball Association
NBA basketball rules wave off any shot that travels over the top of the backboard from behind the basket unit; however, it can count as a field goal if an NBA player working the baseline sinks a jump shot that went over a segment of the backboard. NBA legend Kobe Bryant showcased a premier example of the rule exception in 2009 against Oklahoma City.
He dribble drove the lane, but defensive pressure forced him behind the bucket. Despite his momentum pushing him toward the baseline, Bryant launched a high-arching shot that flew directly over the side of the backboard and landed as a clean swish into the hoop.
International Basketball Federation (FIBA)
The International Basketball Federation rulebook features a rule that distinctly differs from the NBA and NCAA. An offensive player can plant his feet behind the basket without driving to the hoop and legally deliver a shot that passes straight over the backboard. It's only disallowed if the ball touches the basket support, or if the player steps on the baseline and fails to stay inbounds.
Doctor's Delivery
Several famous shots and dunks have come from the other side of the hoop, but perhaps none more so than one from Hall of Fame and perennial all-star forward Julius "Dr. J" Erving. Back in the 1980 finals, the 76ers star took off from behind the backboard and went around several Los Angeles Lakers to deliver a clutch reverse layup. Some people consider it the greatest shot in NBA history.