Twists & Turns of Phrase
When something’s got all the bells and whistles, it has been constructed with lots of extra features—usually ones that aren’t strictly needed. This phrase is often used to describe electronics, motor vehicles, and other complex products.
According to the OED, the bells and whistles in this turn of phrase were originally those found on fairground organs. There are other possible origins of this phrase; however, and Michael Quinion has posted some of them over at World Wide Words.