Stocks

"You would think that the appeal of pelting the same person with fruit would wear off after a while, but, oh, no!"

- Merlin to Gaius Stocks were devices used in medieval times as a form of physical punishment involving public humiliation. The stocks partially immobilised its victims, who were often exposed in a public place, such as the site of a market, to the mockery of those who passed by. Since the purpose was to punish those offenders who acted against the standards of conduct of the time, anybody could assault, revile or aim filth, like tomatoes, at the victim. Merlin often ended up in the stocks, usually because of Prince Arthur Pendragon. The first time Merlin got put in the stocks it was as punishment after mistakenly picking a fight with Prince Arthur over his prat-like behavior towards a servant before Merlin knew he was the Prince of Camelot. From that first meeting with Arthur, Merlin has continued to point out Arthur's prattiness and, once he became Arthur's servant, Arthur has treated Merlin much the same as he treated the manservant Merlin stood up for (and possibly replaced), though over the years their relationship has grown into one of mutual respect, companionable mockery, nearly brotherly affection, and absolute trust. Merlin has ended up in the stocks on several other occasions when covering for Arthur to Uther by taking the blame for Arthur's absence from various events. Merlin also first met Guinevere while in the Camelot stocks for the first time, at which point she praised his bravery and called Arthur a bully (The Dragon's Call).

Dagr was sentenced to the stocks by Arthur after antagonising Mary at her tavern with Ebor for a share in her profits, resulting in a bar brawl when Arthur defended her, during which Gwaine got badly wounded while defending Arthur from Dagr. As a result of his humiliation from being sentenced to the stocks, Dagr swore revenge on Arthur which resulted in him entering a melee with Ebor, disguised as Sir Oswald and Sir Ethan using blood crystals, to try and kill Arthur, however, they were both killed by Gwaine before they could take their revenge (Gwaine). When Merlin attempted to find treatment for Arthur's wounded leg, he disobeyed his order to let him accompany Gwaine and Elyan when looking for Uther and Arthur threatened to have Merlin sentenced to the stocks for that (The Coming of Arthur: Part One).

Trivia

 * Merlin being put in the stocks was a running gag in Series 1, but it has not happened since then.
 * The stock gag was mentioned by Arthur in episode 12 of Series 4 when Merlin tells him to think of something pleasant and Arthur replies "You in the stocks?".
 * Despite the stocks being a notable form of punishment in Camelot, only two known people have been sentenced to the stocks throughout the Series: Merlin and Dagr.
 * The scenes involving Merlin being pelted with rotten vegetables while in the stocks were a challenge because Colin Morgan, the actor who plays Merlin, is reportedly allergic to tomatoes.