Watch Robin Williams's Best Ad-Libbed Movie Moments

Robin Williams possessed the swiftest of wits, the gift of voracious speech, and an endless Rolodex of characters to summon. In every medium he worked, the late entertainer’s mastery of improvisation knew no equal.

For movie actors, going off script is generally a fireable offense. Williams, however, got a rare pass from Hollywood and encouragement to test his own material. Some of Williams’s most famous characters — including the Genie in Disney’s Aladdin — developed as products of his impromptu experiments.

To take one example, Williams improvised the final line in Good Will Hunting, a fillip Matt Damon regards as “Robin’s best addition” to the film. He also created one of Mrs. Doubtfire’s biggest laughs when the frosting unexpectedly melted off of his character’s face.

Take a look back at Williams’s best ad-libbed movie moments in the video above.