Justin Bieber stops by the set to show off some of his Canadian pride, learn about "Humanimals" and what "Popcorning" is really all about.

Floyd Mayweather visits the Ridiculousness studio where Rob shows him what a "Pain Face" looks like. They'll also endure some "Romantic Injuries" and learn "How Not To Train."

Former "PMOY", Sara Jean Underwood, visits the Ridiculousness set, where Rob shows off his "Fear Face" and they talk about how "Cats are Weird."

UFC championship fighter, Quinton "Rampage" Jackson, shows his wolf battle cry and what really sets off his "Hot Button." Rob also shows videos of "Crappy Endings" and what it's like to get "Slampaged."

"Ace of Cakes" star chef, Duff Goldman, stops by set with a scorpion cake and we see some of his "Unnecessary Costumes." He and Rob also show videos of "Grand Entrances" and "Ghost Holes."

Australian radio personality/skateboarder/author/jack of all trades Jason Ellis drops by to check out some bromantic activities and get kicked in the crotch by Chanel live in the studio

The original 'Ridiculousness' trio watch clips of "Random Tackles" and animals seeking revenge, and Chanel swaps places with Rob for some "Redneck Good Times."

'Nitro Circus' stunt warrior Street Bike Tommy joins the 'Ridiculousness' gang to watch the wildest whisky throttles and gutsiest big dudes on the web.

Lil Jon and Rob enjoy the "Yeah" category inspired by the rapper, watch videos of "Dancing Animals," unintentional "Body Shots," and people getting "Fenced."

Tyler, the Creator and Loiter Squad co-star, Taco, visit the set of Ridiculousness and learn about "Sloppy Finishes" and "Faceballs."

Rapper, Wiz Khalifa, guest stars where he'll discuss with Rob why "Grass Is Your Friend" and the joys of "Human Magnets." The fan favorite, "Makeshift Thrill Rides," returns to the show.

Actress and musical artist, Kat Graham, shows us some of her big moments of "One Liners" and how to dance on stage with one shoe. Rob also shows videos of her "Magical Spells."

Drift racing super-star, Vaughn Gittin, Jr., reunites with Rob to watch videos featuring "Faulty Equipment" and "High Speed Chaos." Rob introduces instant classic categories such as "Flailers" and "Stunt Dummies."

Rob shows the audience how to "Escape Your Pain" while friend and pro championship skater, Chris Cole, learns what it's like to be in the "Hot Seat."

Scott "Big Cat" Pfaff helps the host break down clips of outrageous viral videos.

WWE Divas and Bella Twins, Nikki and Brie join the crew to show their "Backyard Wrestling" moves and how to make the perfect "Pain Angel."

Rob, Chanel, and Sterling educate the audience on how to "Save Your Drink," why "Safety Hurts" and see some "Chanels in Training".

MTV host and BMX rider, TJ Lavin, stops by the set to learn about "Shirtless Manplay," "Flinstoning" and "Animal Prodigies."

Rob's parents, Patty and Gene, join the crew to relive some videos of their children's "Pranks," "Sibling Rivalry" and some of Rob's greatest childhood moments.

To honor the season finale of Ridiculousness, Wee-Man and Preston Lacy take to the couch to watch and celebrate upon all the other jackasses in the world.