Border Collie, Echo, who played the beloved dog Nellie in the Netflix series Heartstopper passed away at 9 years, after a sudden diagnosis of brain cancer. Echo's owner, Leonie in an Instagram post revealed that the Border Collie was euthanised on May 18, after his condition deteriorated rapidly. View this post on Instagram Instagram PostLeonie explained that the first signs appeared during a routine walk when he seemed unseady, and vets suspected it was a vestibular tissue. However, his health quickly worsened leading to paralysis on one side, and scans later confirmed that Echo had brain cancer. In the caption, Leonie wrote,"This is a post that I thought I wouldn't be writing for quite a few more years but he(re) I am, 18th May we had to say goodbye to our beautiful Echo, it's taken me a while to write because I didn't want it to be real."Leonie went on to add,"Echo you truly were the best boy ever, you loved everyone and everything, you became famous from starring in the Netflix series Heartstopper and was loved by thousands, I miss your little nudges so much, you were my cuddle monster, thank you for being my Echo."More about Echo, who played Nellie in HeartstopperEcho played the role of Nellie Nelson, Nick Nelson's beloved pet. Nellie in the series is a comforting and affectionate character who is known to accept everyone as they are. In June, 2021, author of the book Heartstopper on which the Netflix series is based opened up about Echo's casting."Echo is a male border collie and he was actually the understudy dog - the original dog was unwell so Echo stepped in to save the day like a true professional! He was ready for his moment in the spotlight!! I can’t wait for you to see all the very adorable Nellie and Nick moments we have in the show 💖🐶"Alice Osman also commented under Leonie's Instagram post on Echo, and said,"I'm so so sorry to hear this 😢 Echo was very special to so many and we will always remember him and all the joy he brought to us! ❤️❤️❤️"Fans of the show took to the post to express their love for the Border Collie. Many claimed that he was their favorite character in the series. Several fans also called the dog the "sweetest boy" and thanked him for playing Nellie and gracing their screens.