You've got to have a likeability factor, I think, in your comedy characters. If the guy's really, really funny but you just don't like him or her, then you're never going to root for them.
Research has shown that one's level of intelligence is the single most predictive component of professional success - better than any other ability, trait, or even job experience. Yet, too often, employees are selected because of their likeability, presence, or charisma.
You can make low-budget film as long as there is something compelling about the characters. There is a believability in the chemistry and a likeability amongst the characters.
In a late-night monologue, it's not just about being funny; you have to come off as knowledgeable. You have to cultivate a persona of trust and intelligence and likeability.
I have this theory that the likeability question comes up so much more with female characters created by female authors than it does with male characters and male authors