The eye-catching figures were on hand to help launch a campaign by NHS Merton Clinical Commissioning Group (CCG) Not Always A&E - asking people to only use accident and emergency in life-threatening situations this week.
The campaign also aims to highlight what it says are quicker and easier alternatives to accident and emergency services where people can get advice and treatment.
Dr Howard Freeman, GP and chairman of NHS Merton CCG, said: "Our Accident and Emergency department is overrun by people experiencing long waits for treatment of conditions that could be handled by many other Merton health services."
The 'yellow giants' are also appearing across Merton on billboards, in health centres and other public buildings.
For more information on local services, visit the website on www.notalwaysAandE.co.uk and enter the symptoms and postcode.