Friendship is one of the best relationships on this planet. It's a unique bond that truly knows no discrimination. Time and again animals have proved that they are indeed humans' best friends.

Here we have listed some of these timeless and special friendships.

1. Dindim, the penguin and Joao Pereira de Souza, the retired mason who once rescued it.

Joao Pereira de Souza, rescued the penguin caught in an oil spill. He nursed the bird back to health, before releasing him back to the sea. Ever since then, Dindim has travelled back to the coast of Rio de Janeiro to be with Joao.

Source: Facebook

2. Hiroyuki Arakawa, a Japanese diver who has been friends with a fish for over 25 years now.

When Arakawa was entrusted with the task of looking after an underwater Shinto shrine he befriended an Asian sheepshead wrasse named Yoriko. Every time, Arakawa visits his marine friend, he greets the fish with a warm kiss.

Source: Boredpanda

3. Dan McManus, professional hang-gliding instructor, has been flying with his dog, Shadow, for over 9 years now.

Shadow is Dan's service dog and you will always see him by his side when flying. In fact, Dan specially made a harness so that he can fly with his dog. Shadow not only gives him company while flying but also helps him manage the symptoms of anxiety.

Source: petslady

4. Mr. Chen and his dog who waits outside a station every day for him to return from work.

Mr. Chen has been with his dog, Xiongxiong, for over 8 years. Every day, Xiongxiong waits for around 12 hours at the station until Chen comes back from work. He then greets his human and leads him home.

Source: boredpanda

5. Mark Dumas and Agee, his polar bear, have been together for around 18 years.

Mark Dumas, an animal trainer, adopted Agee when she was just eight weeks old. And the two share a unique bond. They are not just friends, but family. And you can see Mark and Agee playing, fighting and swimming together.

Source: petsdetective

6. Dolph C Volker and his friend Gabriel, a cheetah hug each other whenever they meet.

Dolph first met Gabriel when he was just 8 months old at the Cheetah Experience Breeding Centre in Bloemfontein, South Africa. He would hand feed Gabriel and the two quickly became friends.

Source: Source

7. Damian Aspinall and his gorilla friend, Kwibi

A video of Damian Aspinall reuniting with his old gorilla friend, Kwibi after over 5 years went viral few years ago.

Source: cbs news

8. Kylie Brown and her duck, Snowflake are always seen together.

Kylie was just 5 when she got Snowflake and the two soon became inseparable. Snowflake believes that Kylie is his mother and Kylie treats the duck like her child.

Source: cbs news

These stories show how love and friendship knows no bounds.