An actual koala is the overall commander of Koala Forest Academy's Sensha-do team.

OVA included in the Blu-ray/DVD release of the fourth Girls und Panzer das Finale film.

The second film in the six-part Girls und Panzer: Saishuushou film series. 
 
After falling for BC Freedom High’s clever deception, the Oarai Girl’s High tank-maidens find themselves faced with an entirely different battlefront than expected. However, Yukari suspects that any bluff that could have been carried out so easily by so many people must have some basis in fact. So, as the other school teams prepare for combat across the competition, Oarai digs down with a plan to undermine the groundwork beneath their opposition. 
 
(Source: Sentai Filmworks)