Spanakopita is an annual festival and holiday, complete with its own set of games and competitions, unique to the Greek island of Spanakos. There is no information available on the internet for it because in reality the festival is a complete sham, held only to gain money from the wealthy Dr. Venture, who attends every year. Regardless of the truth of its origins, the festival represents one of the few things that makes Dr. Venture genuinely happy.
On October 20, 1968, Jacqueline Kennedy was to wed Aristotle Onassis in the Greek islands. Jonas Venture Sr. and Team Venture, along with many other celebrities, attended the wedding. Jonas left young Rusty Venture under the care of H.E.L.P.eR. aboard the X-2.
1968 was a harsh year for the people on the barren island of Spanakos, spurring Giorgios and several of the island's other residents to rob the yachts and boats of the wedding attendees, including the X-2. Among the things they stole was a trunk which the thieves thought was filled with money or valuables, but which actually held Rusty acting out the Trojan Horse. When they discovered Rusty, the inadvertent kidnappers tried to contact Jonas but there was no answer. L. Ron had kidnapped Jacqueline Kennedy, necessitating the intervention of Team Venture; in the process he disabled Team Venture's radio equipment by destroying the X-2.
After three days passed with no response, Little Rusty began to despair, so the kidnappers pretended the kidnapping was a traditional part of a local festival called Spanakopita. Jonas and Team Venture came back three days later, giving Giorgios and the other kidnappers a severe beating before leaving with Rusty. Giorgos vowed to make Venture pay. Strangely enough, twenty years later an adult Rusty returned ready to celebrate the "festival" he remembered so fondly. For the past two decades Rusty has returned every year, paying Giorgos a hefty sum of money each time and in an unexpected way making Giorgos' vow come true. 
In the Venture Bros. episode Spanakopita!, Giorgios officiates the usual games, though with an added new element: Augustus St. Cloud has joined as a contestant, mostly as a means of annoying his hated rival Billy Whalen, who has tagged along with Venture for that year's Spanakopita festival. With the aid of his parkour-skilled servant Pei Wie and a generous amount of money, St. Cloud almost wins, but he is thwarted at the last minute by the efforts of Billy and Pete White. St. Cloud decides to buy the festival outright and ban Team Venture out of spite. However, Giorgios sells him spanakopita the spinach pie rather than Spanakopita the festival.
The festival hosts a number of games, for which the contestants are awarded a certain amount of drachma depending upon how well they do. The person with the most drachma at the end is recognized as the "King of Spanakopita", the winner, and receives the official crown as a prize. The events include:
- A running of the goats race (similar to running of the bulls in Spain mixed with a foot race)
- Diving for sponges
- Pumice-carving competitions
- The original Spanakopita festival was created after Rusty Venture's kidnapping on October 20, 1968. Once three days had passed, on October 22nd or 23rd, the inaugural Spanakopita festival commenced, lasting for another three days.