Le Chat (which, even I know, translates as 'The Cat') was the brand name of René Léger, based in Vitry-sur-Seine, in the southeastern suburbs of Paris.
The brand is known for its front derailleurs. Frank Berto claims that these were introduced in 1931, but the earliest patent I have found is from 1934. Whichever is true they were amongst the first front derailleurs to make an impression in the market. The signature designs were integrated into the downtube in a festival of exquisite brazing - much beloved by modern admirers of vintage French bicycles.
Le Chat appears on this web site because René Léger also patented a rear derailleur in 1934. A particular feature of this derailleur appears to be that it could be used with fixed cogs and with back-pedal brake hubs. I don't know if it ever made it into production.