the important thing about it is if you have 250 trophys, you get a new character and if you have all, you get a special prize.
544
around 544trophies in the whole game!!
There are 554 trophies in super smash brothers brawl (ssbb).
Go to the unlockables section of the trophies and stickers section. Do what its requirements are and you'll get them.
To get 100% on SSBB SubSpace, get everything in every area(trophies,secrets,etc.).
If you mean in the Space Embassy you have to find the trophies and complete the levels to get them back to fight against Tabuu.
you get them the same way as enemies from the subspace emissary, you need to deliver a finishing blow to them with a trophy stand.
All character trophies are obtained by completing classic mode and all star mode.
there is a way without hacking or cheating because i read in the prima offical game guide that you can, but it didnt say how
Play more brawls in group mode and unlock all the characters and collect more trophies and stickers.
If you mean "How do you get R.O.B. on SSBB", then you have to either play 160 brawls, get 250 different trophies, or get R.O.B. to join you in the SSE (Subspace Emissary).
Sonic is in SSBB.