Two kittens whose fur was coloured in with permanent marker are being repeatedly bathed to help wash out the ink.
The four-week-old kittens, called Shrek and Smurf, were found in Bradford and are being cared for at the city's Cat Watch Rescue centre.
Volunteers have been bathing the kittens in the hope of washing out the stubborn blue and green ink.
Several well-wishers have also offered to take the kittens into their homes.
Volunteer Katie Lloyd said: "It's been really busy, the phone has not stopped, but the care of the kittens is paramount.
"I am sure in the future we will have no problem re-homing them."
The kittens had been coloured in with a very dark royal blue and an emerald green.
Ms Lloyd said: "They are black and white kittens and all the white bits had been coloured in. Its horrific, and meticulously done.
"We have to be very careful to ensure that the ink does not go down their nose or throats or in their eyes.
"But I am fairly confident that over time the colour will completely come out. If not by washing then it will grow out."
The kittens' plight has attracted global attention and also prompted an American author to set up a donation page to help with their care.
New York-based Gwen Cooper, who wrote Homer's Odyssey: A Fearless Feline Tale, said on her Facebook page that making a donation would show that "most humans are caring and compassionate".
She said she hoped to raise around $2,000 (£1,370) and early on Wednesday had pledges of $1,336 (£915).