For around 38 years, the McDonald's Happy Meal has come in a red box with those arched handles and a big smiley face on it.
However, in a major change to the design, the smile has been dropped as part of an effort to let children know it's alright not to feel happy all the time.
It's currently Mental Health Awareness Week and McDonald's have commissioned research which warned that 48 percent of British children feel like they have to be happy all the time, even if they don't want to be.
The study found that 74 percent of parents believe it's important to stop their children from feeling sad, and 63 percent of grown-ups say they encourage their kids to always be happy.
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The redesigned Happy Meal box is supposed to help communicate to kids and their parents that it's alright to talk about things that are making you unhappy.
As a result, McDonald's has dropped the smile from their Happy Meal boxes and replaced it with the message: "It's okay not to feel happy all the time."
Around 2.5 million of these boxes have been made and sent out to more than 1,400 McDonald's locations across the country, and they'll be containing Happy Meals served to customers between 13 and 19 May.
This campaign has been done alongside Children in Need, and has set up a hub of content for families to access so they can have honest conversations with their children about feelings.
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The hub can also be accessed via a QR code on the Happy Meal box.
One of the supporters of the campaign is former Manchester United and England footballer Rio Ferdinand, who said: "I've experienced first-hand with my own children how good communication and encouraging kids to embrace how they truly feel can build trust and help to manage emotions - no matter how big or small.
"It's our job to empower our children to express themselves freely and support them every step of the way in understanding that it's okay to not be happy all the time."
Louise Page, McDonald's head of consumer communications and partnerships, hailed the moment to highlight the mental health of children.
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She said: "We’ve been proudly supporting BBC Children in Need for four years now, and we know how important it is to help stimulate open conversations about mental health in families.
"Through this change to our iconic Happy Meal box, we hope that many more families are encouraged to kickstart positive conversations around children’s emotions and wellbeing."
Children in Need's director of impact and influence, Fozia Irfan OBE, said: "Mental Health Awareness Week is the perfect opportunity to shine a light on the vital impact we can make on children and young people’s mental wellbeing and we are thrilled to be working with McDonald’s to provide the necessary support parents and families may need to start the conversations with their children."
Topics: McDonalds, Mental Health, Food And Drink
Joe Harker