Magna Doodle

Invented in 1974 by Pilot Corporation,[1] over forty million units have been sold to date worldwide, under several brands, product names and variations, including Tyco and Mattel/Fisher Price.

The key element of the toy is the magnetophoretic display panel, filled with a thick, opaque white liquid containing tiny dark magnetic particles.

These particles can be drawn to the drawing surface by a magnet-tipped stylus or optionally provided shapes, or removed to the hidden back side by a sliding eraser bar.

This led to Pilot suing Mattel unsuccessfully in 2004 for infringement of its trademark and trade dress, while relicensing the brand to the Ohio Art Company.

In the TV comedy Friends, a Magna Doodle is visible in Joey and Chandler's apartment, with various messages written on it throughout the series, referencing plot points, current events, inside crew jokes, or just random drawings.