From the yeah, really department: In February 1942, the Japanese mounted the first mainland attack against the United States since the War of 1812, and the attack was likely prompted by prickly pear cactus spines stuck in a Japanese fellow's ass.
In the early months of World War II, ten Japanese submarines patrolled the west coast of the United States. In 1941 and 1942 they sunk about a dozen ships, sticking to targets at sea. But Kozo Nishino, the commander of I-17, a 350 foot long B-1 class submarine 70 feet longer than the largest German U-boat, decided to up the ante one evening in February 1942. He surfaced off the shore of Ellwood Oil Field, near Santa Barbara, California, with his crew of 101. For twenty minutes, starting at about 7:15 pm, the I-17 fired 15 to 20 shells at the facility.
After the attack, Captain Nishino reported to the Japanese command that he’d “left Santa Barbara in flames,” but the shelling was kind of a bust. The Japanese had the best shipboard night optics in the world at the time, but most of the shells fell either well short or well beyond the intended target. The attack caused about 500 dollars worth of damage to the oil facility pier, and there was only one injury reported. (That injury actually happened well after the attack, when a worker was injured while trying to defuse an unexploded shell.)
Nishino knew the area well. In the 1930s, he’d often captained a merchant tanker in and out of the Santa Barbara channel, sometimes loading crude oil at the Ellwood oil facility.
During one such visit in the late 30s, officials invited Nishino ashore for a welcome ceremony. While walking up the path to the ceremony location, he fell into a prickly pear cactus, and cactus spines were pulled from his butt while oil field workers looked on and laughed.
As legend goes (it’s a widely accepted story, but not without dispute), Captain Nishino never forgave the folks at the Ellwood facility for laughing at him, and would years later seize the opportunity to gain revenge from a Japanese submarine. Thus, the probability that the first mainland attack against the United States since the War of 1812 was provoked by a prickly pear cactus--and laughter.
The attack on Ellwood could be viewed as kind of a joke, especially since the jitters brought on by the attack almost certainly led to the so-called “Battle of Los Angeles” the next day. Decades later, the two events would inspire the movie “1941.”
But in the longer term, the hysteria provoked by the attack was no laughing matter. It led to greater censorship of the news, and increased pressure to confine Japanese-Americans and Japanese visitors in internment camps. Soon, 110,000 Japanese people--62% of them U.S. citizens--were forced to leave homes and businesses behind and were confined to internment camps.