In the scene at the end of the movie when they are on the way to get Aerosmith tickets, it shows Simone and Slater in the back seat. Both windows are down, and the wind is whipping through Simone's hair. They then show Slater sitting beside her blowing perfect smoke rings from the joint they were smoking. No wind whatsoever. I love those magic smoke rings!
When slater is smoking in the car on the way to get the tickets, you can very plainly see that he does not blow smoke rings at all. Smoke rolls out everywhere. What are you blind?