Oh yeah. I remember Amsa is one of the play testers.
He's not the only one IIRC:
*
9B: played
extensively and discovered new ways to chain-throw people to death. Consistently a top 5ish player in Brawl and reached #1 in 2014, as evidenced by
this retroactive ranking.
*
Ranai: Most famous for his
stint, where he consistently placed well in international tournaments. Ranked top 30ish during
2016 and 2017.
*
Earth:
and
player, ranked top 20ish in 2016. Might be the only player that's undefeated against MewtwoKing in multiple games interestingly enough. Yes, they only played one tournament set in each game (Brawl and 4), but it's worth noting that MewtwoKing is the only player to be retroactively ranked #1 in multiple games in the same year (
Melee and
Brawl, 2008).
Point being, those four brought a lot of knowledge of past games and mechanics.
For the record, Gamma showed up twice in games in playable roles even after his death.
The first one was in Sonic Shuffle, where he was revived by the power of dreams (since that game takes place in the world of dreams and they wanted an excuse to have the entire SA1 roster present.)
So Sonic Shuffle decided to trap an explosion-proof bird inside a robot's head again through the power of dreams? Real smooth.
(FTR, I don't have anything against Gamma - I like him because that bot's got a pretty good character arc. I just find Omega funnier personally.)