Spike was a bit too comfortable being a dog

[cider float 2,535]

I mean due to his nature in Equestria, he seems to have assumed the role of a puppy dog really quick now that I saw parts of the first movie again.

[cmarston1 5,951]

He was too busy dealing with Twilight's mental breakdown about becoming a different species to have his own.

[Buck Testa 5,503]

In equestria he is a servant with a ton of chores and responsibilities. He's tugged between the pony world and his own heritage. He constantly has to struggle between Greed built into his very nature and the Generosity that was nurtured into him. 

 

In the Eqg world, the only thing he needs to do is act like a pet. I dare say that's a vacation for the little guy. 

[cider float 2,535]

He was too busy dealing with Twilight's mental breakdown about becoming a different species to have his own.

I mean he liked getting pet by Twilight and wanted Rarity to scratch behind his ears in a very intimate way.

[Crystalline Star MLP 9]

He was! But he had to help Twilight sooo...

[ManaMinori 4,143]

When Twi is freaking out, he's able to ignore his own issues, to be the voice of reaon for Twilight. He's comfortable with being a dog because Twilight's worse off, and unable to deal with it, and so Spike puts her concerns before his own, and just doesn't think on it too much to worry about himself

[Red Cedar 1,406]

Remember the scene in Rainbow Rocks during the slumber party? When he's got Fluttershy cuddling him like there was no tomorrow as they slept? Yeah, he's not gonna complain.

 

As someone else mentioned, he probably thought being able to just pretend to be a dog was a vacation considering what Twilight puts him through.

[twiia 1,842]

Hes a bit too comfortable as a dog because he doesn't really need to do anything (except eat and sleep)

[Life Fiber Infused 41]

I mean he liked getting pet by Twilight and wanted Rarity to scratch behind his ears in a very intimate way.

 

After this fact i accept the headcannon that Spike is a submissive

[Midnight Seashell 206]

What's cool is him being that small dog and every girl wearing skirts

Edited April 23, 2016 by Midnight Seashell

[Ziggy + Angel + Rain 11,298]

I don't see what's wrong with that; I'm perfectly comfortable being a doge.

 

 

Something horrifying that my friend cooked up for me. xD  He insists I point out that's it's only an "alpha version."

 

 

[Angus McFife 14]

Yeah, I mean Twilight could hardly move around as a human, and Spike is just fine. Maybe there's evidence somewhere that he's used to dealing with living in a different form?

[silvadel 1,393]

There is just something about the innate instincts of a dog. 

[Moon Sugar 532]

It's probably easier being a pet than a friend slave. (lol)

[nightshroud96 116]

It kind of bothered me that he completely brushed aside the issue of he doesn't get to be human there.
With how its really unfair, how it hinders him and the fact it implies he's more of a pet to Twilight and others than equals to them.
In the long-run, he shouldn't brushed that aside honestly..