It was Nelvana.
The only Mad Dog character I'd say was grandpa with all his "Yo Tyson!" "Keep it on the down-low G". The dub has more issues regarding characters that never existed (Dizzy, Brad Best, and AJ Topper are all dub-only characters), and some questionable edits rather than casting. The casting for the main cast was pretty decent, it was a nice change of pace that they actually hired children to play the roles of well... children.
Nelvana's worst dub (this means audio quality, not so much adaptation quality) is Bakugan. The quality of the show in any language is pretty poor, but the script, and acting in that is very bad.