What is the title of the 2006 Pixar short featuring Mater and a ghostly legend?

The 2006 Pixar short featuring Mater and a ghostly legend is Mater and the Ghostlight.

The short follows Mater after the other residents of Radiator Springs play a prank intended to frighten him. They tell him about the Ghostlight, a mysterious blue light associated with the town, and the joke leads to a supernatural-looking nighttime encounter.

Mater and the Ghostlight was directed by John Lasseter and Dan Scanlon and released as a bonus short connected with Cars. It expands the first film's setting rather than continuing the main feature's racing plot.

The title is sometimes confused with Cars Toons episodes such as Rescue Squad Mater or Tokyo Mater. Those later shorts are part of a different series of Mater-centered adventures. Mater and the Ghostlight is specifically a standalone short associated with the original Cars era.