Notable for his work in the band Atomic Rooster, he is probably best known for his role as the ill-fated drummer Mick Shrimpton in the film This Is Spinal Tap.

[2][3] By the end of 1971 he had been invited to rejoin Atomic Rooster, this time staying long enough to play on the band's last two albums.

[2] After Atomic Rooster folded, Parnell (using his nickname "Spyder") joined with the Italian group Tritons, who had a hit in Italy with their re-arranged version of the Rolling Stones song "Satisfaction" in 1973.

[3] After leaving Nova, Parnell continued to play for various other bands and artists throughout the 1970s and 1980s including Michael Des Barres and Lisa Dal Bello, as well as providing the drums for the Toni Basil hit "Mickey" among other contributions.

His character was one of a long line of unfortunate drummers who all perish from freak accidents, his own fate being spontaneous combustion.

While living in Missoula, Montana, Parnell co-hosted an 8-midnight radio program, Spontaneous Combustion, on KDTR Trail 103.3 FM.