Say what you want about their odd celebrations, the goblins do provide a lovely boost to the sales of gunpowder.
The Drathden Goblins celebrate birthdays in a rather rigorous way. Firstly, a birthday cake is required - but not the usual confection of cake and icing favoured by humans, no. The cakes made by the goblins are immense constructions (compared to the small goblin stature, at least) with thick walls and a hollow internal cavity, accessed usually by a panel of cake that can be removed.
Into these cavities, as many explosives as possible are placed. Bombs, caskets of gunpowder - anything that will make a satisfying boom. You can see where this is going - so can they. The cakes are sealed, iced, decorated, and brought into the town's (slightly charred) celebratory square on the eve of the goblin-in-question's birthday; often there will be multiple, or particularly large cakes, to celebrate multiple birthdays.
The 'birthday goblin', as they should be referred to, is then led to the square armed with a weapon of their choice. Whether it be flaming arrows, trails of string to be lit by matches, or a concoction fondly referred to as 'Molotov's Cocktail', their weapon is one intended to light the candle-shaped fireworks atop the cake - and to thus set off a show of fire and fireworks, lighting the square and causing sweet chunks of cake and icing to spatter all gathered goblins (and outside visitors).
Much celebration follows, obviously - and depending on the amount of alcohol consumed, many
an explosion follows too!