Twiggy is the code name of Apple's own proprietary 5.25 inch floppy disk system named after a 1960s fashion model (Twiggy) who was famously thin. It was designed to be a higher-performance alternative to the Disk II and Disk III floppy systems used on the Apple II and Apple III personal computers. Twiggy drives were introduced with the Apple Lisa computer in 1983, and were used in prototypes of the Apple Macintosh line of computers. But they quickly ran into difficulties due to unreliable performance and incompatibility with industry-standard diskettes. They were replaced at the last minute by 3.5-inch diskette drives built by Sony.