US Army personnel playing baseball on Bougainville.

Some good stories from Werner Hermann on Quora:

During the Pacific war on the islands of Bougainville in the South Pacific, American and Japanese forces clashed with each other. The American invasion of the island was intended to be a mop-up operation to eliminate Japanese forces stationed there. Thanks to American air and naval superiority that made possible the island-hopping strategy, the operation on Bougainville was of little strategic value.

Consequently, in a bizarre and little known turn of event, neither side had any incentive to seek confrontation against each other, because the Japanese could not win and the Americans no longer needed to fight for total control of the island, the armies of both sides settled into a pattern of co-existence. This was when some strange and funny events occurred.

For example, in the 37th Division area, one infantryman recalled that at a company baseball game:
Someone noticed a raggedy-assed Jap way out in the shadows of the jungle off right field watching a game…. He came back for other games and was soon a rather regular fan… The 37th GIs figured “he can’t be all bad”; besides, he somehow managed to root for 37th teams, showing his approval of hits and runs for the home team!

In another event, a Japanese soldier infiltrated the US camp to watch movies. When a captured Japanese film showed the sinking of the USS Lexington, he gave himself away:

There suddenly came shouts of “Banzai! Banzai!” from the tangled but huge branches of a banyan tree on a near side of the row of seats… [he] was overcome with patriotism at the sight of his comrades in the air force sending an enemy ship to the bottom! He was pulled from the tree … Perhaps the last victim of the carrier Lexington.

ROTFLOL. Poor fellow. That guy should have known better to keep quiet when inside enemy-held territory. He could have saved himself.