It was revealed in the 10th volume of light novel Overlord
(pictured) that the series will be receiving an OVA. It will be bundled with the 11th volume and is scheduled to ship on September 30. The OVA episode will contain new footage from the Overlord: Ple Ple Pleiades
chibi anime short series with 30 minutes of content.
Overlord: Ple Ple Pleiades
is a comedy short series that featured super deformed version of characters from the original series.
Source: Animate Times
Overlord: Ple Ple Pleiades (OVA)