I noticed this was mentioned in an old quiz in these forums back in '03, so as it appeared in today's papers, decided it was time for a refresher. "If you ever need reminding how stupid the human race is, just read the story of the Pastry War. Even its name gives you a clue: yes, the war really did start over pastry. In 1832, a small bakery in Tacubaya, near Mexico City, was damaged during some civil unrest. Its owner, a Frenchman, wrote to Louis Philippe, the King of France, calling for action. The King duly demanded reparations of 600,000 pesos from the Mexican government (the daily wage of a workman in the country at this time being one peso). When no reply was forthcoming, Louis Philippe sent a war fleet to blockade the coast of Mexico and bombard a fortress. The Mexicans tried to get round the blockade by smuggling in supplies from the Republic of Texas. Authorities there tried to prevent this, and in one raid seized 100 barrels of flour. To this day, that part of Texas is known as Flour Bluff. No fewer than six nations were involved at various points, and the war cost 127 lives and left 189 wounded. One of these was Antonio de Padua María Severino López de Santa Anna y Pérez de Lebrón (really), whose leg fell victim to French grapeshot and had to be amputated." How six nations went to war over pastry | Daily Mail Online
So, if I understand this correctly, the Texans aided the Mexicans who went to war over a Frenchman's Danish.
The pastry war is on a par with The 1778-79 Potato war - or Plum Fuss War of the Bavarian Succession - Wikipedia The war of Jenkins' Ear 1739-48 War of Jenkins' Ear - Wikipedia The 1969 Football War Football War - Wikipedia
I think my favorite it the "Pig War" The Pig War of 1859 - The Pig War Perhaps that's because in the end it was handled rationally and the only casualty was the pig.