In between rehearsals, Honey G, whose real name is Anna Gilford, recorded an impromptu rap in support of the brave children and their families being cared for by the charity.
She also chatted to them and told them her and mentor Sharon Osbourne were like "two peas in a pod".
Honey G also took the time out to sign autographs and have her photo taken with the families, along with the other contestants, judges and host Dermot O'Leary.
“It was brilliant to have the families from The Brain Tumour Charity here," said Honey G.
She added: “It has been an incredible experience and I’m loving every minute of it.
“The X Factor judges and team are amazing. Sharon is a brilliant mentor and texts me a lot.
“We’re like two peas in a pod. I’m so grateful to everyone who’s voted for me.”
Children watched on as she was put through her paces by Mrs O ahead of last Saturday's movie night theme when she performed a mash up of Will Smith’s Getting’ Jiggy Wit It and Jason Nevins’ It’s Just Like That, which for the first time landed in her in the bottom two.
She then went on to survive the sing-off against Ryan Lawrie on Sunday (November 20) night.
Rosie Rickards, 15, from Andover, Hampshire, who was diagnosed with a brain tumour at 11 and has been cancer-free for three years, said: “I can’t believe that last Saturday I was watching Honey G on my TV and now I’ve met her.”
Mrs Osbourne also recorded a short and sweet message for the charity and the children.
Watch Mrs O's message to The Brain Tumour Charity and their families
Emma Percy, children and families services worker with The Brain Tumour Charity, said: “We are so grateful to Honey G and The X factor for such a fantastic welcome and special day.
“It gave the children and their families a chance to relax away from their daily stresses and has created magical memories for them.”
Now Honey G is getting ready for Saturday’s night’s "Louis Loves" theme as she competes against Matt Terry, Emily Middlemas, 5 After Midnight and Saara Aalto, for a chance to be one step closer to the final.
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