Doug Legacy (b. 1954) is a musician and one of the founding members of the the Zydeco Party Band. He has puppeteered background characters on Muppets Tonight and his band were featured as the house band for the show (with Legacy playing accordion). He made a cameo in episode 207 and did the whistling in the "Muppets Tonight Theme".
His band, the Zydeco Party Band, also won an Emmy for being the house band for The Late Mr. Pete Show. The band also provide music for Gilmore Girls, How I Met Your Mother, and The Bucket List starring Jack Nicholson, Morgan Freeman, and Sean Hayes.
Outside of the band, Legacy plays a pirate at Disneyland playing sea shanties on accordion and penny whistles.