can u unlock all the characters from this mode? also can u do so on one run thro, thnx

If I remember correctly, there're some characters that cannot be unlocked by Subspace Emissary, such as Toon Link. You do get a majority of them though.
And yes, it's definitely possible to finish the Subspace Emissary in one go. My friend and I sat down and played for around 8 hours straight and beat it.

kk kool, do u mean u unlock all the possible characters in one go? also, i saw on gamefaqs u unlock toon link thro the forest stage on there or something?

Yup, at least I believe so. When I beat Subspace Emissary, I unlocked all the ones that we meet in the stage in the process.
And from my knowledge/source:

kk well ill just have to wait and see i suppose

Only 3 characters you have to go back to unlock, toon link (forest), wolf (ruins), and jigglypuff (swamp i believe) everyone else you get first run through. you can also unlock them by playing different amount of vs. matches etc.

ah kk thnx m8, i knew i saw summink bout link and the forest lol

Yeah you can unlock all the characters in SSE. Those 3 that vox leet mentioned are the correct places.

Here's a tip to unlock all the characters in pretty much 30 mins. to an hour.

Go to special melee, put on stamina mode and the flower hat only

In the character select screen right after choosing the options for special melee, put stamina for you and a cpu at 1%. As soon as the game begins both of you will instantly due to the flower hats dealing instant damage and only having 1% life. Just keep pressing start and restarting games and you'll have the chars in no time.

my friend told me about this, never tried though casue in mele sudden death killing didnt count