Growling Means “No”
The trick to the successful adlib is complete transparency. If the audience is able to tell the character left script it loses its flare a bit. The producers of Black Panther swear by the scene where M’Baku cuts off CIA agent Everett Ross by grunting like an animal.
T’Challa’s mother Ramonda calls for the aid of M’Baku, leader of the Jabari tribe. When the bold CIA agent tries to interrupt, he is met with assertive grunts and growls. Director Ryan Coogler described the dash-off as an animalistic and aggressive dismissal of any further involvement from Ross. Shut ‘em down, boss!