The Venture Bros. – Season One 
A recurring theme in the first season of The Venture Bros. was a series of dreams Dr. Venture would have where one fetus (with facial hair like himself) would attack another fetus (also with hair) in the womb. This began in the pilot episode before the creators knew where it would eventually lead them. The dreams were explained in the season finale, “Return to Spider-Skull Island”.
The Venture Bros. – Season Two 
The second season’s storyline picks up from Hank and Dean’s accident, as well as The Monarch continuously attempting to reunite with Dr. Girlfriend who is in a relationship with Phantom Limb.
The Venture Bros. – Season Three 
On February 26, 2007, at the New York Comics Convention, Jackson Publick announced that Cartoon Network had ordered third and fourth seasons of the show. A portion of a rough cut of “The Doctor is Sin” aired April 1, 2008 as part of an unannounced April Fools’ Day sneak peek at upcoming shows.
Season three of The Venture Bros. reveals more backstory and character histories than the previous two seasons. A recurring issue deals with the history of the original Team Venture, as well as the death of Jonas Venture Senior. This season also touches upon the nascent and unregistered arching of Rusty Venture by the Monarch.
The Venture Bros. – Season Four [2009-2010]
The fourth season of The Venture Bros. premiered on October 18, 2009. Production began in June 2008 and overlapped production of season three. The season aired as two sets of eight episodes, with the first eight beginning on October 18, 2009 and the next group of eight premiering September 12, 2010.
The first half of the fourth season revolved around Dr. Venture’s interactions with his new bodyguard, Sergeant Hatred; Hank taking Brock’s absence poorly; Henchman #21 dealing with the death of Henchman #24; the return of Phantom Limb; and The Monarch’s resurgence as Dr. Venture’s primary nemesis. This season also saw the introduction of ancillary characters Captain Sunshine and Monstroso, both of whom were referred to as early as the first season.