[12] In his senior year, Mullen was a National Merit Finalist and fourth award winner at the Intel International Science and Engineering Fair for a team project with his future wife, Cathy Chen.

[12] Both he and his wife received the Jim and Donna Barksdale Scholarship to cover the full cost of attendance of medical school.

[16] Mullen has held world records in 12 different memory sport disciplines, with the majority-minority of them involving the memorization of numbers or playing cards.

[36] Mullen was a two-time contestant on the final season of the Chinese television program The Brain in 2017, defeating his opponent Wang Feng, the 2010 and 2011 World Memory Champion, by accurately recalling the airline routes, departure and arrival locations, and times of 50 flights.

[38] Mullen has been featured in The New Yorker,[39] BBC,[40] CNN,[41] The Washington Post,[42] Lifehacker,[43] Vital Signs with Dr. Sanjay Gupta,[44] Today,[45] Mic,[2] Guinness World Records,[46] Men's Health,[47] The Guardian,[48] and The New York Times,[49] among others.