Doing a Henry Winkler/Ron Howard/Gabe Kaplan mashup: Mortal sin or cardinal virtue?
While it is normally considered a grievous affront not to balance out the various universes used in this alchemy, I will note two things:
1) Ron Howard's stint on The Andy Griffith Show is a mitigating factor, and
2) Gabe Kaplan's hair will soothe any astral mishaps that may bubble up from Winkler's dark, dark soul.
That much said, I make my ruling:
MORTAL VIRTUE.