Tarantino's screenplay originally had the film told out of order ala Reservoir Dogs and Pulp Fiction. In the original script Clarence dies in the end, and Alabama goes on to work in crime meeting up with Mr. White from Reservoir Dogs.

Kahuna burgers are mentioned in Pulp Fiction, From Dusk Till Dawn and in True Romance too. When Clarence (Slater) takes his first bite of the Kahuna burger, he has almost the exact same reaction as Jules (Jackson) has in Pulp Fiction when he takes a bite of Brett's burger.

Source: http://www.jonhs.com/