In the 25 years since his debut on Nickelodeon, SpongeBob SquarePants, the animated character who lives in a pineapple under the sea, has also appeared in video games, three feature films, and even a Broadway musical. For the voice actors behind SpongeBob and other denizens of Bikini Bottom, the show – a gentle, silly reminder about the value of optimism and friendship – also reminds us of the kid inside us all. Lee Cowan reports.