"Captain Good" is the default mode
Most Jekyll & Hyde cases, including the Trope Namer himself, have Dr. Jekyll as the default mode. In fact, in this cartoon, the Trope Namer looked like Captain Good before drinking his (in)famous potion and becoming a dead ringer for Phantom Phink. He created the "Phantom Phink" persona to do evil deeds that wouldn't be traced to "Captain Good".- "Captain Good" is the form he uses when he joins the other racers at the start line.
- "Captain Good" is the real person and in a freak experiment, he is transformed into the Phantom Phink, but we do not have an origin for "Clean Kat"/"Sinister Sludge", his behavior points at Sludge being the real being while Clean Kat is the disguise.
"Phantom Phink" is the default mode
He usually tries to win the races as "Phantom Phink" unless that identity is disqualified and the "Captain Good" persona is his only way to remain in the race. Captain Good once was a real hero
He wouldn't be the first good guy in animation to have a Face–Heel Turn. However, unlike other former heroes, he created an alter ego to do his evil deeds so he still could enjoy the reputation his past heroics earned him.