Using a string double bass played with a bow could definitely add a comedic element to your music. While it might not be as common as the tuba for comedic effect, it can still work well, especially if you play with the dynamics and articulation to make it sound quirky or exaggerated.
As for specific examples of funny double bass parts in musical numbers, they might be a bit more challenging to find, as the tuba is often chosen for its more overtly comedic sound. However, that doesn't mean you can't create something unique and funny with
the double bass! You could experiment with pizzicato (plucking) as well, which is more commonly associated with comedic effect in string instruments.