Jaleel White -- CLOWNIN' DONALD STERLING ... At L.A. Courthouse

Donald Sterling was NOT the most famous person at the L.A. County Superior Courthouse this week ... that honor went to Jaleel White ... who hilariously RIPPED on the Clips owner right outside the courtroom and TMZ Sports has the footage.

White appeared in court as a witness in someone else's legal battle -- at the same time the Sterling media circus was underway in the same building.

So, Jaleel being Jaleel ... thought it would be funny to fire off some Donald Sterling trash talk -- and he was right.