The show had been in negotiations among the Tiswas stars for around 2 years before it was finally agreed upon. The plan was that if all agreed, they would go ahead. If a single person disagreed, they wouldn't go through with it. The BBC aired 'It Started with Swap Shop' in December 2006, making it appear as though ITV rushed out a copycat idea, despite 'Tiswas Reunited' being conceived back in early 2005.
Chris Tarrant correctly asserts that Tiswas beat Swap Shop by being the first feature-length Saturday morning children's television show in the UK, thus nullifying the 'It Started With Swap Shop' claim. Tiswas began in January 1974, and Swap Shop began in October 1976 as a direct result of the BBC suffering ratings decline to ITV in the midlands. However, the first UK Saturday morning children's television show began in September 1973 - 'Orbit' aired only in the HTV region.
One of the original format ideas for the show was 'An Audience With Tiswas', in the same vein as other 'An Audience With...' shows by ITV/LWT. By January 2007, the plan had morphed into 'Tiswas Reunited'.
This was not the first Tiswas reunion. The ITV Telethon 1988 had the major Tiswas stars get together in the early hours of the morning for around 20 minutes, re-enacting sketches, putting celebrities in the Cage. This took place Studio 1 at LWT studios, where Tiswas Reunited was also filmed. Like Reunited, this reunion culminated in a recital of the Bucket Of Water Song, although this took place outside the studio building on the street.
To fill up the Cage, the producers approached fan website TiswasOnline to ask for volunteers. Nearly 100 Tiswas fans applied. 10 were chosen, with a few stand-bys on hand. On the night of recording, the production team noted that 14 people could fit into the Cage, so some of the stand-bys were used.