As part of the 'I Heart Harold' campaign run by the official Neighbours website, international stars including Tom Jones, 1980s popstar Rick Astley and WWE wrestler John Cena have joined Aussie celebrities The Wiggles, Australian Idol judge Ian 'Dicko' Dickson and Smith's former co-star Natalie Bassingthwaighte in leaving messages of support.
"I was never going to give you up but you're off anyway - best of luck," said Astley.
A 'We Heart Harold' group has also been set up on facebook, with more than 800 fans already signing up.
Smith, 70, quit the soap last August after 22 years on screen. His final scenes aired in Australia on Friday.
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