The 'Weetabix. Fuel for Big Days' spot is BBH's first work for the cereal brand since winning the account in March.
The 30-second and 60-second ads feature each member of a family, including the toddler, explaining their day ahead over a bowl of Weetabix, in a series of flash-forward sequences.
The ad will run nationwide over the next few months, supported by radio ads, social media and YouTube activity.
The ad's creative directors were Dominic Goldman and David Kolbusz. Kolbusz was also one of the ad's two copywriters, with Ed Cole.
Goldman and Lewis Mooney were the ad's art director and Guy Shelmerdine was the director.
Adrian Mooney, head of marketing at Weetabix, said: "Weetabix stands for different things for many consumers and we embarked on a key project to find that one defining piece of insight which differentiates the brand within the cereals category.
"We want Weetabix to own that 'Big Day' moment. Our aim is for Weetabix to be front of mind for consumers when they think about preparing for their busy day."
Dominic Goldman, creative director at BBH, said: "The fast pace of modern life can be exhausting and yet it's typically English to wear your busy day like a badge of honour.
"We leveraged this insight and created a game of one-upmanship centred around the breakfast table, where a family compares notes whilst fuelling up with Weetabix to prepare themselves for the big day ahead."