The actors name is Bob Dishy. Cigargeorge makes some good points. The character did seem to be written in because he was familiar with the modern methods and technology while Columbo wasn't. In the episode Last Salute to the Commodore Columbo was assigned another young protege named Mac. Not really sure what his purpose was but it was a quirky episode anyway

Dog will always be the ultimate sidekick for Columbo. The two of them were so wonderful together.....they were both so sweet........