The delightful Karen Gillan (twitter.com/karengillan2) of Doctor Who and the upcoming films Oculus and Guardians of the Galaxy returns to the program this week to help Matt, Jesse and Andy celebrate the 100th episode of Probably Science, covering a wide range of topics including: Matt’s electrical problems! Andy's sugarfree gum-loving rats! The wonders of the number 100! Ab inflation! A message from Brooks Wheelan! Why does no one remember that Jesse lives at Bluebell? Karen hanging outside with the cool kids! Karen’s upcoming horror film Oculus! Sheltering child actors from the terrifying movies they’re in! Children’s innate belief in immortality! The excommunication of Halley’s Comet! Matt and Andy’s trip to the trampoline park! Early humans picking up bad genetic traits by mating with Neanderthals! The Scottish royal mental asylum! Jonas Salk’s 100th birthday and the history of the polio vaccine! Rutherford’s atomic discoveries of 1914! The 100th anniversary of the gun synchronizer! Dipping blood cells in acid to make stem cells! Non-hormonal, reversible, cheap male birth control! The Addams Family electric shock game! Karen’s stint in a Coney Island freak show! Karen’s horror movie scream abilities! The chart of English larval progression! Competing listener donations! Stephen Hawking’s black hole update! Our upcoming live show on the topic of sleep! Greatest hits from our first 100 episodes!