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-born actor and radio personality, Jason Ellis, shows us he is an expert at Showing Off Gone Wrong when the introduction of Tramp Stamp videos earns him a surprise payback from Chanel.

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.

Rob's cousin and Fantasy Factory co-star, Scott Pfaff (AKA Big Cat), comes to the studio so he and Rob can demonstrate why Birds Are Dicks and how to Get Froggy.

Guest stars WWE Twin Divas, Nicole and Brianna, stop by the Ridiculousness set to show us some of their Backyard Wrestling moves and how to make the perfect Pain Angel.

Sterling and Chanel help the host break down clips of outrageous viral videos.

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

Rob's parents, Patty and Gene Dyrdek, come by set to watch videos revisiting their children's Pranks, Sibling Rivalry, and some of Rob's best 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.