Comedian/actor/voiceover artist Valerie Tosi (@valerie_tosi) joins Andy and Matt (and Roo) to discuss Andy’s dogsitting business, whale dissection, Boston accents and pirate accents, Cheddar Man the early Brit, when humans first left Africa, potholing/spelunking, kids performing better when they're Batman, oil patterns on bowling lanes, SpaceX success, and blowing up their near misses, vaping risks and clove cigarettes.

Actor/improviser Lauren Flans (@laurenflans) of Another Period, Wild 'n Out and the new podcast Tell Us We're Funny and We'll Go Away joins Matt and Andy to discuss travel credit cards and Mexican drugs, Orphan Black, anti-abortion teachers, legislating numbers, different infinities, '70s poison toys, radioactive Fiestaware, Gerrymandering and its origins, a fake RHCP song, lasers that can rip apart empty space, whales that talk, elephant painting, Svengali and Machiavelli, poisonous toad-eating crows and quokka pics.

Comedian/actor/writer Kiran Deol (@shitfromkiran) joins Matt and Andy to help celebrate the six-year (iron) anniversary of the podcast and discuss crashing astronomy conferences, shooting Prince Rupert’s drops, breathing oxygen at depth, predator/prey turning, chalk and cheese, monkey clones, celebrity pet adoption, crow hooks, space lungs and yucca injuries.

Comedian, star of Those Who Can't and frontman of the band SPELLS Ben Roy (@benroy00) joins Matt and Andy to talk about Andy’s accessibility, Poison songs, evolutionary psychology, the books The Mating Mind and The Righteous Mind, space growth, living underwater, cell phone risk, bats melting in Australia, frozen alligators, gila monster saliva helping diabetes, and bonobos liking jerks.

Comedian Ricky Carmona (@RickyCarmona) of the podcast Who Shot Ya? joins Andy and Matt to talk about when to say Happy New Year, Weird Science vs. Real Genius, how to stop superbugs, raw water, the other John Snow, laser eagles, slowing down light, power plant mirrors that explode birds, things deadlier than sharks and parking mathematics.

Friends of the show TJ Chambers (@TJChambersLA) and Auggie Smith (@AuggieSmith) return to kick off 2018 with TJ and Andy's new podcast Twinsies (@twinsiespod), space beer, monkeys bonin’ deer, the recent SpaceX launch, traveling salesbees, sleeping jellyfish, Matt Walker on sleep (and on Probably Science), how to keep your exercise resolution, and Tommy Wiseau’s surprise tenant.

Matt’s on the road in Colorado and meets up with his old university friend Dr. Pete Newton (@newton_pete) who's now an assistant professor at the University of Colorado, Boulder to talk about his TEDx Talk on why "food miles" are aren’t all they’re cracked up to be, his journey away from and back to academia, safari tours in Botswana, hunting pangolins, anaconda attacks in the field, the perils of ruminants, changing our behavior, changing a whole country’s behavior, and whether you’d eat lab-grown meat.

Matt and Andy make a visit to the home of Jim Jefferies (@jimjefferies) to talk about a very British car accident, self-driving cars, Ted Danson's amazing face, feeding spiders graphene, a new space tire, Mars temperatures, cricket commentary, onion ubiquity, Dubai space agriculture, business class from the ground, and upsetting rock stars.

Host of the Rock Solid podcast Pat Francis (@pat_francis) joins Matt and Andy to talk about donating medals, miming phones, teen brains that can't tell what's important, homeless etiquette, Voyager I firing up again, coffee and health, grammar rules and beard posturing.

Comedian/musician Eli Braden (@EliBraden) joins Andy and Matt to discuss jazz addicts, the flat-earth rocket guy and his earlier flight, conspiracy theories, not a head transplant, prehistoric women's strength, why boning is heart-safe, mnemonics, grossing out chimps, health codes and California D.