There's an old joke that most Jewish holidays are based on the same premise: "They tried to kill us, we won, let's eat!" In my mind, the holiday that best matches this scenario -- and possibly gave rise to it in the first place -- is Purim . It also tends to be the most fun holiday, with kids (and increasingly often their parents) dressing in costumes and lots & lots & lots of audience participation and loud noises actually encouraged during the service.
For those readers unfamiliar with the holiday, here's Purim in a nutshell: In the ancient Persian empire, Queen Esther (whom the king does not know is Jewish) and her uncle Mordecai discover and foil a semi-secret plot by viceroy Haman to kill all the jews in the kingdom. There are enough plot twists and complications to make an excellent movie or mini-series -- but the modern-day fun comes from dressing up as major characters in the story and making LOTS of noise every time Haman is mentioned during a reading of the story in synagogue. The "let's eat" part of the holiday comes after the service, with special pastries called "Hamantaschen" (with many other possible spellings) featured as a special treat. Hamantaschen are triangular to mimic the supposed shape of Haman's hat, and while classically filled with sweetened poppy seeds they are also frequently filled with chocolate or fruit preserves.
Since the Pipsqueak is part of the synagogue's kids' choir, her participation in the holiday service was a foregone conclusion -- so she and Mommy started planning her costume well in advance. After some false starts, they latched onto the idea of the Pipsqueak dressing as a Hamantaschen. I had some big rolls of brown craft paper I'd saved from Amazon shipments, so AJ applied some creativity -- along with a bunch of colored paper, tape, and markers -- to turn one of them into a giant wearable Jewish pastry for her daughter. (Sorry; this is the only photo I have of the costume that doesn't violate AJ's guidelines for Pipsqueak photos online.)
The crafts were followed by a BYO dinner which was itself followed by a short period of chaos as tables were rolled out of the room and rows of seats were set up. The rabbi (who was as much into having fun with the holiday as any of the kids) eventually managed to get things down to a low enough roar to start the actual service. After some songs from the choir, baskets filled with groggers were passed around and I'm glad to say they were put go good use by one and all. In keeping with the fun attitude, the rabbi kept the story of Esther extra-entertaining by using the projection system so the congregation could read along... with each slide embellished with the likes of minions, the Big Hero 6 crew, smurfs, Lego Movie characters, and the like.
Once the story reached its end (and the groggers were collected for use again next year, much to the relief of the parents present), it was time for the costume parade! Despite an amazing similarity to the annual rounding up and herding of cats from the lowland pastures to their summer grazing grounds in the mountains, the rabbi & helpers managed to get all the kids in costume (along with several costumed parents) sort of lined up and moving along parallel paths.
Unlike the days of my youth, when such events only included characters drawn from the Story of Esther (leading to a parade of dozens each of Hamans, Esthers, King Ahasueruses, and assorted ancient warrior-type guys), the parade also included several video game characters, a couple of cowboys, a nurse, enough Marvel & DC superheroes to protect several planets, a handyman, a fireman, and, of course, a hamantaschen. Oh, and a rhinoceros -- I kid you not. (He was only about 4'1" but a rhino nonetheless.)
The parade wound around & through the sanctuary and out into the lobby, where a grand assortment of baked goodies & drinks waited to help celebrate the holiday. One highlight of the celebration was the rabbi coming up to Miri, taking one look at her yellow-centered costume, and exclaiming, "An apricot hamantaschen! My favorite!" (Yes, we like the guy.)
 As you will see, the holiday is becoming something of a "Jewish Halloween," with costumes of pop culture figures increasingly supplanting the classic depictions of biblical characters from the story.
 Groggers are ratchet-based noisemakers that one spins around to make a racket. They, along with lots of booing, are enthusiastically employed at every mention of Haman's name during the reading of Esther's story.