The gang's all back together again to celebrate 300 episodes of Probably Science while discussing barely any science at all, instead reminiscing about the last six years, getting nostalgic for Country Summer and trying to figure out which actors have achieved the coveted SPATS (piloting a spacecraft, plane, automobile, train and sea ship on film).

Dean Burnett (@garwboy) is a neuroscientist, comedian, blogger and author of the new book Happy Brain: Where Happiness Comes From, and Why, and he Skyped in with Matt and Andy to talk about the book, delving into the complex relationship that happiness and human brains have with work, love, fame, home, humor, aging and much more.

Comedian, writer and host of The Cracked Podcast Alex Schmidt (@alexschmidty) joins Matt and Andy to talk about 3D printing, Gategate, phone facts, the English Larval Progression, Andy and Matt's recent Cracked appearance, eels on coke, black holes eating stars, cane toad sausages and lonely radiation bacteria.

Comedian Mitch Burrow (@MitchBurrow) joins Andy and Matt to talk about boot camp morning alarms, blueprint-building and 3D thought, deaf schizophrenia, Moshe Kasher’s book, exploding head syndrome, cold water calorics test update, the unluckiest guy in Pompeii, why Guatemala’s volcano is more dangerous than Hawaii's, all life on Earth by mass (and what we did to destroy it), The Cove documentary and Mitch’s podcast “We’re With Them."

Astrophysicist and professor at University of Rochester Adam Frank (@AdamFrank4) joins Matt and Andy to talk about his new book Light of the Stars: Alien Worlds and the Fate of the Earth, a look at the history of scientific discoveries on planetary environments and the prospect of alien life, what the very high likelihood that extraterrestrial civilizations have existed in our universe can teach us about the fate of human life on Earth, how an inevitable growing pain of any civilization is climate change and what to do with that information to ensure that our civilization survives its cosmic adolescence.

Comedians and hosts of the upcoming Good Job You Failed podcast Vana Dabney (@vanawrite) and Deborah Etta Robinson (@deborah_etta) join Andy and Matt to discuss human echolocation, marsupials fucking themselves to death, death by fart smell, nerve regeneration (or lack thereof), the longest paths on Earth, non-detectable neutrinos, Deborah and Vana's podcast and bodybuilding goals. Watch Matt's clip on The Jim Jefferies Show here or here.

Comedian and writer Jesse Joyce (@jessejoyce) joins Andy and Matt to talk about taxidermy, muskoxen, takins, red panda poop glitter, Qinling pandas, Gavin Webster's pandas, Bitcoin's energy usage, Jesse's dislike of live music, pouring warm and cold water in your ears, bad company names, patent trolls, discovering animals, Snoop's pinecone and the mysterious return of ozone.

Comedian Robyn Morrison (@RobynSomething) joins Andy and Matt to discuss concert height etiquette, the best sciences on drugs, more aphantasia, snail memory, science trivia questions, sitcom tropes, Korean nukes, thermal tasters, hippo shit and drowning wildebeest.

Neuroscientist/comedian Ori Amir (@OriAmir) joins Matt and Andy to talk about putting Matt in an fMRI, how your brain constructs jokes, prosopagnosia and aphantasia, politics and the brain, what computers find easy and hard, AI and game-solving, and more about Uber's bad driving. Plus, fill out this survey and we might go on a cruise together!

Comedian Brett Erickson (@iBrettmypants) joins Matt and Andy on location at the Jim Jefferies Show offices to talk about meeting Slayer's guitarist Kerry King, Oliver Sacks' book An Anthropologist on Mars, Temple Grandin and her hug machine,  aphantasia, penis transplant updates, New York water updates, DNA findings leading to the Golden State Killer, caterpillar danger, Globetrotters facts, an instrument to help reveal faint exoplanets, the Retro Encabulator, The Freeze, and large spleens.