LogFAQs > #963859186

This is genuinely one of the best (more or less improvised) performances Ive ever seen from Will Smith. Buthe broke character (-2 points for a total of 8/10) right after the slap (which itself was real but made to look harder with Wills telegraphed hit and Chris enhancing the impact a little to much)

https://youtu.be/2QU1hIyqW6E

Notice in the clip that Chris is getting ready for the slap by adjusting his feet position and leaning forward with his hands behind his back.
Then, Chris yells WOW in true Chris Rock comedic fashion as a briefly smiling Will almost cracks up (15 second mark) but then keeps his head low in an attempt to avoid too much attention to the details.

Back on the seat, Will goes all in with his stellar acting and turns on tears like regular people turn on the tap for water (pro actors do this all the time in rehearsals).
Will Smith tearfully delivers standard by-the-book Hollywood politically correct acceptance speech to a cheering crowd whos already forgotten the slap. The show goes on like nothing happened, like The Smiths family smile and pose for the press after the show, as if nothing happened.
Both Will and Jada are great actors and masters at garnering attention for millions of views.

Also, the Slap Trick has been done before:
https://youtu.be/FL9PGJslS6A