But that was just the way pupils at Warrington and Karitane schools liked him when he took them for a science lesson yesterday - in rap.
Microphone in hand, the rapping biologist took learning to a different level for the group of about 50 when he rapped about water molecules, curiosity, DNA and problem solving.
After graduating from Stanford University with a degree in human biology in 2008, Mr McFadden spent two years as an instructor in the Human Biology programme.
The infectious nature of his teaching methods have resulted in his videos being a hit on YouTube, and his being written about in the New York Times and Britain's Guardian newspapers.
A Genetics Otago and Otago Institute-sponsored trip to Dunedin for the New Zealand International Science Festival, allowed him to share his "contagious passion for biology, rap, and making science fun".
"I think young Kiwis possess the right combination of a sense of humour and scientific curiosity to embrace the world of science rapping," he said.
Along with this week's tour of schools in Dunedin and Oamaru, Mr McFadden will perform his science rap at Wall Street Mall at noon on July 9.
Children will also be encouraged to make their own science-themed rap during a four-day workshop next week.
The best rapper will become the nation's first Science Idol, at the finale during the Fun and Food Fiesta on July 11.
Mr McFadden will return to Dunedin next year, on a Fulbright Scholarship, to study for a master's degree in science communication at the University of Otago.
