Quick way to get characters:
1.Got to special brawl
2.select the health option
3.put the flower on
4.select the characters
5.select stage
6.wait 1-3 seconds then battle is over
7.keep reapeating 4-6 to get all characters
or just cmlete the subspace emissary and go to the forest stage and ruin stage.

Hehe. This trick is quite useful, but it takes a long time. I would suggest completing the Subspace Emissary (adventure mode) to get all the characters. It will only take about an hour tops.