"Expert or Liar" is the sixteenth episode of Season Eighteen, and the 266th overall episode of The Jumping Ground. It first aired on May 6, 2015.
Lance wants to redeem himself by winning on "Expert or Liar."
The scene opens on Lance weeding the Park's flower garden. He is approached by an elderly woman who commends him on his work, she asks if he is an expert on flowers. Lance boasts that he is indeed an expert on flowers. Hearing this, the old woman unzips what turns out to be a full body suit to reveal none other than Chink Chuckman, the snarky, yet charismatic host to the popular game show Expert or Liar. Apparently the show runs by having Chink disguise himself each week and question random people on their level of expertise. Anyone claiming to be an expert would be immediately quizzed on the subject they said they have knowledge on. True to the show's namesake, if the contestant gets any of the ten questions wrong they are branded a liar on national TV.
At Rob's House, PuffPuff, Zowie, Rob, Clyde, Toad and Jimmy are watching the broadcast alongside a visibly disgruntled Lance. On TV Chink asks Lance what colour violets are, to which Lance answers "red". Of course, he gets this wrong and is promptly branded a liar before getting beaten up by the game show crew. Cut back to the lounge and Lance's colleagues are now laughing at the screen, much to Lance's chagrin. Determined not to let his public humiliation slide, Lance vows to get back on Chink's show and prove he's an expert at something.
The next day at school, Mr. Brown shifts Lucy Powell over to SG-1 in order to rebalance the teams following Douglas' death in the previous episode. Lance then asks Mr. Brown if he can go the toilet in which he says yes to.
Lance later starts packing food from the cafeteria for his lone quest. Puff questions his friend on how he intends to find Chink since the man is always in disguise. Lance answers with full conviction that since Chink's costumes are really lame, all he has to do is find the weirdest looking person on the street and try to pull their face off. Puff warns him that sounds like a terrible idea but Lance would have none of it. He states that he's sick of not being taken seriously and he's not coming back until he finds Chink.
So Lance spends the day going around screaming "Chink Chuckman!" at bewildered strangers before trying to pry their faces off, noteworthy individuals including an old man, a mime, an ice-cream man, a construction worker, a horse and Manslaughter from the episode The Inside Job' who gives him a black eye. As it turns out, none of them were Chink Chuckman. Back at Stamford Gate, Peter Mandelson is not pleased to find his students had been getting into the snack bar supplies. However he changes his tone after hearing about Lance's humiliating run-in with Chink's show from Puff. Mr. Brown goes out in search of Lance and eventually finds him passed out from exhaustion in a seedy part of town.
Lance wakes up after being brought to Mr. Brown's apartment and his boss expresses sympathy for his situation. Mr. Brown reveals that he too was humiliated on National TV some years ago, and he had the tape to prove it. In the video, a younger Mr. Brown was a contestant on a game show called Say That Word. Making it to the final round and one word away from winning $100,000, Mr. Brown screws up the last word by reading "banana" instead of "bandana". Losing his chance at the money, he instead received a bandana with the word "loser" labelled on it while the studio audience jeers him in the background. Recalling those dark days when people use to hand him bananas every time he left the house, Mr. Brown resolves that no one else should have to suffer like he did and offers to help Rigby win back his dignity on Chink's show. They decide that Lance could focus on sandwiches as his topic of choice this time round. Lance ponders on how they were going to find Bert, but Mr. Brown assures him that he'll handle it.
The next day, after receiving a message from Paul, Mr. Brown tasks the other students with finding Chink Chuckman for Lance by going to all the sandwich shops in town. While they were initially unconvinced, Mr. Brown manages sway everyone by reminding them of the times Lance lied to cover for them when they were in trouble. Melvin offers to link them up with his friend Cody, who works as an intern on Expert or Liar, since he might know where Chink Chuckman will be next. So Mr. Brown, Zowie and Lance go to visit Cody while the rest of the gang hit the sandwich shops.
At the Expert or Liar headquarters, Cody allows his guests to look through the upcoming episode files. They discover that there were no sandwich related episodes, instead Mr. Brown finds a file on an upcoming episode that will be set at an arcade. Encouraged by the prospect of being tested on video games, Lance agrees to tackle the challenge head on. Cody brings up a problem; Expert or Liar does not allow repeat guests. Lance however, has a plan.
At the arcade, a tall human gamer is approached by a tubby guy who asks him if he’s an expert on video games. As soon as the gamer discloses he is an expert, the tubby guy unzips himself to reveal a disguised Chink Chuckman, just like last time the camera crew appear out of nowhere and being filming. To Chink’s surprise the gamer pulls his own trick back on him by unzipping his costume and revealing himself to be Lance (who somehow managed to look completely inconspicuous in a much larger full body suit.) Lance demands to be let back on the show, he’s supported by Mr. Brown and a chorus of other past game show contestants who’d all been publically humiliated on national TV. Chink relents, but reveals that this episode is the season finale and is being broadcasted live as they speak. We cut to the Park where Puff, Zowie, Melvin, Jimmy and Clyde are tuning in from the lounge. Chink threatens Lance that if he loses a second time, they will re-run the episode as long as the show's still on air (which will happen for a long time because the show's rating are good).
Bert transports Lance and himself to the gaming centre, which is set out like a side-scrolling platform game. Lance must climb his way to the top, while answering ten game related questions that will get him past the inbuilt obstacles. Chink flies to the top via a floating platform and beings the trivia questions, many involving games that’d featured previously on the program, including Xtreme Xcape (The Serpent's Venom), Strong Johns (Poor and Stupid), The Hammer (Whale Whores), Dig Champs (Fear Factor Phony), and Lemonade Stand (Canada on Strike). Lance aces through them up to question nine and manages to cling to the last beam as the rest of the platforms fall away. As his contestant holds on for dear life, Chink menacingly poses the final question: Who defeated Lord Shinnok in the aftermath of the Battle of Abydos? Lance says it was the Ancients. Chink says that's the incorrect answer, and calls him a liar. But still remembering the events from Homecoming, Lance says it was originally the Ancients, until he and Puff defeated him, until he was resurrected in Resurrection. Lance takes the game, which somehow gives him the ability to fly. He goes up and decks Chink Chuckman in the face which causes the game show host to fall off the platform and be eaten by a pixelated version of Shinnok, which then explodes. As Rigby revels in his victory, Mr. Brown looks on proudly near the audience stand while eating a banana.
Back at home, the guys cheer Lance on over the television. When Zowie mentions that Lance was lucky that didn't go for sandwiches, Clyde suddenly realizes that Toad is missing. Then we cut to Toad attempting to yank a burger suit off a bystander, showing he's still looking for Chink Chuckman, unaware that Lance changed topics.