Phineas and Ferb is a 15-minute Disney animated cartoon aimed at young children, intended to foster creativity, a sense of adventure, and a love of learning in children. It succeeds on all fronts, while being well-written enough to appeal to children while also entertaining their parents. It started in 2007 and was created by Dan Povenmire and Jeff "Swampy" Marsh.
Phineas and Ferb are step-brothers very close in age, whose parents married a few years before the show starts. What happened to their missing biological parents is never addressed. They are as close as blood brothers and share the same interests, namely, spending their summers building impossible contraptions for the amusement of the other neighborhood children, or simply to achieve some goal, like building the world's tallest skyscraper (it reached the Moon). Their construction projects and the effects they have on the neighborhood comprise the A story for most of the episodes.
Construction projects include a roller coaster through the entire city of Danville, a snow skiing hill (yes, over summer vacation), a monster truck arena (converting the family car to a monster truck to participate), a massive, multi-story haunted house (which starts a creepy giant floating baby head running gag), and a portal to Mars. Unfortunately, the educational opportunities are sadly missed during these projects, they'd be a great way to sneak in lessons about things like kinetic energy and how electricity works, but it does showcase the fun of constructive rather than destructive pursuits.
Older sister Candice is constantly trying to get Phineas and Ferb in trouble by showing their mother the expensive and potentially dangerous projects they're building, but she always fails, the evidence being erased by some improbable means at the last minute. Local nerd Baljeet, school bully Buford, and Fireside Girls troop leader Isabella Garcia-Shapiro help out in exchange for being the first to try out their constructions.
Meanwhile, a B story runs alongside the construction projects in which their pet platypus, Perry, is really a secret agent working to foil the plans of Dr. Heinz Doofenshmirtz, incompetent wanna-be supervillain and mad scientist focused on conquering the tri-state area. Although his projects are every bit as ambitions (and impossible) as Phineas and Ferb's, they're pointed toward destructive ends which typically backfire on him. His projects include the Age Acceleratorinator, Slaveinator, Drillinator, and Freezeinator (notice a pattern?), most of which wind up accidentally destroying the evidence of Phineas and Ferb's projects. This is, by the way, just fine with them, because the fun is in the building, not the keeping.
Perry the Platypus is assisted by Major Monogram, who runs the agency he works for, and Doofenshmirtz is aided by his giant robot man, Norm, and sometimes his obligatory beautiful daughter, Vanessa, whom he has partial custody of following his divorce.
The show heavily features running gags and lots of character-based humor. The characters are surprisingly well-developed for a kid's show, and parents will find as much to love about the show as their children will, including parodies and lampshading of common movie tropes and plot devices that will likely go over the heads of their kids. Phineas and Ferb currently has a 7.7/10 rating on IMDb.
Phineas and Ferb has its own fan-created wiki at:
http://phineasandferb.wikia.com/wiki/Phineas_and_Ferb_Wiki