Mine is David Baddiel. Ready? :
“What, Daavid Baddiel?”
More? OK. Hold on to your hats:
“Yes hello I’m David Mitchell”.
Not sure how well this works in print but believe me they are very good and my family gazes at me with affectionate wonder every single time I do them. One trick is to say the name of the person you are mimicking. This leaves the audience in no doubt over who it is and allows them to relax into laughter.