Will Smith saved a young fan from choking to death after a surprise birthday joke went wrong.

The rapper and movie star was shopping in Los Angeles when a fan spotted him and asked him to surprise his girlfriend, who was dining nearby.

Smith agreed and sneaked up behind the burger-munching teenager and started singing 'Happy Birthday' to her. The poor girl was so shocked she started choking.

Smith performed the Heimlich manoeuvre and the girl spat the lodged burger onto the counter of the burger joint.

He then signed autographs and completed his 'Happy Birthday' song before making his way out of the diner.