Say a Smash game released on the GBA in 2003/2004. Make a 16 character roster for it.

[The DanMan]

Inspired by/shamelessly ripped off from a topic I saw on gamefaqs earlier. This is just a what-if exercise if Smash had branched out onto handheld much earlier (technically, the GBA does have enough buttons: the directional pad with tap jump, should buttons for shielding/dodging and grabbing, and the A and B buttons for normals, specials, and A+B for smash attacks) with a more limited roster and features. Who would you pick for a roster of 16 characters? For limitation's sake, base it on Melee's roster (that is, no 3rd parties or characters who'd later become playable).

Here's who I'd go with:

1. Mario
2. Luigi
3. Bowser
4. Link
5. Ganondorf
6. Captain Falcon
7. Kirby
8. Fox
9. Pikachu
10. Mewtwo
11. Blaziken
12. Yoshi
13. Samus
14. Mr. Game and Watch
15. Isaac
16. Roy

>Overall slant is obviously towards handhelds
>Majority of the original 12 is there, with the exclusions happening for the following reasons: Ness had nothing to do with the system until the Mother 1+2 release shortly before Mother 3, and Jigglypuff had flash-in-the-pan popularity in Japan which was its entire reason for appearing in Smash in the first place
>Roy but no Marth due to the first point
>Mr. Game and Watch represents Nintendo's first handheld games, so I think he fits
>Blaziken is there as a newcomer because of Gen 3
>Isaac is there as a newcomer because of Golden Sun's moderate success on the GBA during that time

[serifAizawa]

Personally I'd drop Isaac, Blaziken, and Mewtwo in favor of Marth, Jigglypuff and Ness, and drop Roy in favor of Eliwood, Lyn, Hector, or Ephraim. 

[Fire Emblem Fan]

1. Mario
2. Luigi
3. Bowser
4. Donkey Kong
5. Link
6. Vaati
7. Samus
8. Kirby
9. Captain Falcon
10. Fox
11. Pikachu
12. Yoshi
13. Lucas
14. Lyn
15. Isaac
16. Mewtwo

[Perkilator]

1. Mario

2. Donkey Kong

3. Link

4. Kirby

5. Samus

6. Yoshi

7. Pikachu

8. Samus

9. Captain Falcon

10. *Blaziken

11. Luigi

12. Roy

13. *Lyn

14. Mr. Game and Watch

15. *Bowser Jr.

16. *Wario

Edited September 1, 2018 by Perkilator

[Alistair]

Spoiler

1. Mario
2. Luigi
3. Peach
4. Bowser
5. Donkey Kong
6. Link
7. Ganondorf
8. Zelda
9. Samus
10. Captain Falcon
11. Pikachu
12. Mewtwo
13. Blaziken (the more-or-less breakout character of Hoenn).
14. Marth
15. Hector (replacing Roy and chosen over Eliwood and Lyn because he would offer a bigger difference between himself and Marth imo)
16. Isaac

[NinjaMonkey]

1. Mario

2. Donkey Kong

3. Link

4. Kirby

5. Samus

6. Yoshi

7. Pikachu

8. Samus

9. Captain Falcon

10. Jigglypuff

11. Luigi

12. Ness

13. Bowser

14. Peach

15. Mewtwo

16. King Dedede

[Lord_Brand]

Only four more characters than Smash 64? I'd at least try for a roster of Melee's size. But I'll try to meet the topic's challenge. Rather than just pick four characters from Melee and shove them in here, I'd choose a handful of new faces designed to promote major GBA titles. Worth noting that Mega Man Battle Network, Mega Man Zero, Castlevania: Aria of Sorrow, Final Fantasy Tactics Advance, and Sonic Advance were all major third-party GBA titles at the time, so leaving third parties out excludes some of the most notable releases on the platform. Assuming 2004 for the largest possible selection:

• Mario
• Donkey Kong
• Link
• Samus Aran
• Kirby
• Yoshi
• Fox
• Pikachu
• Luigi
• Ness
• Captain Falcon
• Jigglypuff
• *Brendan/May (Pokemon Trainer-esque trio of Grovyle, Blaziken, and Mudkip, to represent Pokemen Ruby and Sapphire)
• *Lyn (Representing the GBA Fire Emblem)
• *Isaac
• *Fawful