Wikipedia
The MacCharlie was a hardware add-on for the Apple Macintosh that was made by Dayna Communications. The name refers to an IBM PC advertising campaign of the time featuring Charlie Chaplin's " Little Tramp" character.
It allowed users to run DOS software for the IBM PC by clipping on a unit to the chassis of the 128K Macintosh, as well as a keyboard extender to provide the function keys and numeric keypad that were absent from Apple's original keyboard.
The clip-on unit sat to the side of the Mac and, like the contemporary Amiga Sidecar, contained essentially a complete IBM PC compatible with an 8088 processor, 256K RAM (expandable to 640k) and a single 5.25" floppy drive that stored 360K. A second floppy drive could be added.
While running DOS software, users could still access the Macintosh menu bar and desk accessories. MacCharlie used the Mac as a terminal, performing all DOS processing itself, and sending video data over a relatively slow serial link to the Mac for display. This slowness, coupled with the declining prices of real IBM PC compatibles, contributed to the short market life of the MacCharlie.