Pretty sure Jeff's correct in that Goten's shirt says "Son" because it's his full name, though in most English dubs the surname is dropped and they're just known by one name.
Kai uses Son Goku at least once, but they're weirdly adverse to using his full name. I even saw an interview with Sabat where he went out of his way to emphasis that though they were acknowledging it now they weren't going to throw out the full name that often.
Jason is bad at it and pinning his own shortcomings as a player on the game. It's pretty fun once you get used to how the combat works, and actually comprehend the tutorials the game gives you like how to choose what finisher to use.
When he said "I don't want a boss to actually dodge or block my attacks" you can tell this game isn't for him. Probably better off with Dynasty Warriors or something.
It's amazing how in the comments for a podcast where two people haven't seen Dragon Ball before and experience it for the first time, people assume everyone has seen Dragon Ball before and can just post whatever they want.
Roll referring to Mega Man as just "Mega" seems like somebody on the translation team doing a Ctrl+F, replace all "Rock" with "Mega". I think the PSP remake of Mega Man 1 did the same thing.
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