"Whatcha talkin bout Willis" is a phrase that originated from the TV show Diffrent Strokes, which aired from 1978 to 1986. The phrase was popularized by the character Arnold Jackson, played by Gary Coleman, who would often say it to his older brother Willis, played by Todd Bridges. The phrase has since become a popular meme and catchphrase, often used to express confusion or disbelief.
While the exact wording of the phrase can vary, the most typical form of the catchphrase is "Whatchu talkin bout, Willis?". However, the name sometimes varies based on the situation, and it is sometimes used with other names or without a name at all.
There are several videos on YouTube that feature the phrase, including clips from Diffrent Strokes and other TV shows, as well as parodies and remixes.