Struggling slacker Foster Sabatini is the only member of his circus family who left the life, greatly disappointing his wealthy father Max Sabatini (of The Flying Sabatinis). When Max dies, Foster and his sisters (who all hate Foster) are shocked to hear that Max left his entire estate to Foster, but only on the condition that Foster can care for his father’s beloved trio of orangutans. Along with the orangutans, Foster also inherits the services of Lazlo – Max’s manservant & protege. The arrival of the orangutans and Lazlo turn Foster’s life upside-down, all while he attempts to win back his disgruntled girlfriend and impress her high-society mother. All during the film are non-stop instances where the apes wreak havoc on Foster’s quiet and simple life with their crazy and outrageous antics, while Lazlo continuously recites many quotations from Max (always ending with “Love Max”).
Things are further complicated by a trio of bungling assassins hired by the local zoological society, who will inherit both the money and the orangutans if one of the apes dies. In scenes reminiscent of the Three Stooges, each attempt by the hitmen is foiled by the apes and results in the hitmen injuring themselves instead. Foster and the others are completely unaware of the attempts on the apes (until the end, when the frustrated hitmen barge in and take the apes by force), and try to keep order despite the mischievous behavior of the orangutans.
Once aware of the danger to the apes, Foster and his friends must save the newly accepted primates from their captors and bring the assassins to justice.