I happen to like this phrase which gets it's origins from the UK. If you're not familiar, it is used to describe something that would be a simple set of instructions such as:
"Gather up all the ingredients, put them in a bowl, mix, and Bob's your uncle, you have cookie batter."
I was curious one day where exactly why/how the term came to be. Come to find out there isn't one explanation that has been decided upon as the one true origin. A quick search of wikipedia reveals these possible origins:
"A common explanation is that the phrase dates to 1887, when British Prime Minister Robert Cecil, Lord Salisbury decided to appoint Arthur Balfour to the prestigious and sensitive job of Chief Secretary for Ireland. Lord Salisbury was Arthur Balfour's uncle.
Another explanation is that it is related to the British General, Lord Roberts, nicknamed "Bobs." The British Army in India coined the term, "Bob's your uncle" to indicate you had the good fortune of being related to the commanding general.
There have been several other slang expressions which included the word "bob," some associated with thievery or gambling, and, from the eighteenth century on, it was also a common generic name for someone one did not know. The difficulty with any of these explanations is that—despite extensive searching—the earliest known published uses of the phrase are from 1932, two from 1937, and two from 1938. (See these and other quotes in American Dialect Society list archived posts by Stephen Goranson."
Anyone from the UK want to weigh in? Funny that such a great phrase has no concrete origin that has been agreed upon.