There's an important thing to know about working with comedy double acts and it goes like this: one of them is quirkier, more eye-catching or just plain funnier than the other. As a producer your initial contact with the Double is via the other one - the pretty/straighter/more accommodating and approachable one. But beware - let them know this is how you see it and the relationship can quickly sour. They can decide this is how it is - you can't. So don't give all of the funny stuff to one half of the pair cos in this day and age NOBODY WANTS TO BE THE ERNIE.
Like I say - nobody wants to be the Ernie - nobody, it would seem, except this compliant Muppet.