Responding to the appeal, Stormzy wrote: "Happy birthday Ollie! You're a lil legend. ️️Don't watch the bullies they always end up being the biggest wastemen later in life."
Others included TV presenter Jake Humphrey, who recorded a video where he told Ollie to "ignore the haters", adding "we've all been there".
Broadcaster Sara Cox also posted a video message to Ollie.
Other famous names who sent well-wishes to the schoolboy included:
Australian film star Russell Crowe
Strictly Come Dancing champ Ore Oduba
Comedian Jason Manford
Astronaut Tim Peake
US actor Wil Wheaton
BBC Newsround presenter Ricky Boleto
Actress and comedian Dawn French
The England football team
Simpsons character designer Eric Keyes
Many offered to send Ollie gifts or free tickets for events.