Is there some kind of connection between the fictional characters Karen Walker (Megan Mullally) (from NBC's Will & Grace) and Bernadette Rostenkowski (Melissa Rauch) (from CBS's The Big Bang Theory)?

For example, both characters have high-pitched voices that aren't their respective actors' natural voices.

I do agree that Bernadette and Karen sound similar. They both have unseen relatives. Karen's husband Stan was never seen on the show and Bernadette has her mother-in-law in voice only.