Sabrina, the Teenage Witch episodes aired regularly during SMTV Live. As a recurring joke, Dec had often proclaimed his love for Sabrina and would regularly read a dreadful poem he'd written just for her, often to the dismay of everyone in the studio. In the early days, Ant would attempt to block this by claiming that Sabrina's lawyers had banned Dec from reading out the poem on the air.
Later sketches saw Dec write a story in which he would be the hero that saved Sabrina (played by a female guest from that week's show) from impending doom, but the 'cast' would always ruin it for him, for example, Cat and Ant would mishear words in his story (e.g. When he said the word eastward, a cowboy would come out, with Cat claiming she thought he said Eastwood). Dec also appeared to not be aware that Sabrina was a fictional show, which was demonstrated when Jenna Leigh Green was a guest when Dec treated her with contempt and continually called her 'Libby' despite her protestations that she was simply an actress.
When interviewing Sabrina actress Melissa Joan Hart for the programme, the gag was again employed. Dec asked Hart to be his 'lass'. Apparently not understanding him, she said yes. After this, Dec expressed his intention to share his knowledge and experience, giving rise to the Dec Says sketches.