Why does Pinkie Pie have a strong relationship with Rainbow Dash?

[MLPForLife 55]

I always wondered why Pinkie Pie and Rainbow Dash have such a strong friendship?

[Will Guide 21,367]

For one thing, they share a love of Pranks.

[Megas 28,002]

They love pranks, colorful and extroverted, outgoing and full of energy

[ggg-2 3,554]

Short answer: She's Pinkie.

[Lucky Bolt 35,125]

They have a lot in common, personality wise. I think they just click well. 

[Sepul-Coloratura 764]

I think It's because nobody in the Mane Six are physically active and adventurous as much as those two. Maybe Applejack is the exception, but her and Pinkie together are just less dynamic to be honest.

[cuteycindyhoney 13,325]

6 hours ago, MLPForLife said:

I always wondered why Pinkie Pie and Rainbow Dash have such a strong friendship?

because they are friends. It's the magic of friendship, after all!

[Cash In 22,872]

They have a very good dynamic. It makes sense, given that they both have outgoing and energetic personalities, which work great in tandem with one another

[Appledash4ever0 13]

Its probably because they have lot of things in common and i always thought about this, that they been with each other ever since g3. so i kind of get why they made them so close as like super best friends forever. spending with each other for many years. you can't break them. and how g5 made pinkie a peagsus which made them both EVEN closer, like sisters or forever ever friends. its like, rain with out a cloud, or a rainbow without its color, cotton candy without its sweet sugary taste, and many things that i can say.

[Splashee 28,589]

Pinkie Pie is randomly placed with any of her friends. It think it was just a few episodes where she was with Rainbow Dash, and that was mostly to do Road Runner type episodes. Then she was also tied to the Apple family in Season 4.

[EpicEnergy 23,240]

Because they like each other's personality! Honestly, I don't think they need to have anything in common to have strong relationship.