It's the hottest day of the year and the zoo's keepers are busy delivering ice lollies to keep the animals cool. The baboons, elephants, and lions are all loving their icy treats, but Gorilla Island seems to have been mysteriously missed off the keeper's ice lolly list. Silverback Jurgen is getting seriously hot under the collar at the oversight until an unexpected rubbish bin turns up and it is keepers Matt and Craig's turn to get hot and bothered.

It's seven years since Jurgen arrived at the zoo and each year he celebrates his anniversary, or 'zooniversary', by putting on a show, whether the zoo animals like it or not. This year he is planning a live music concert - the bunting is up, the fireworks are ready and Dave has been practicing his guitar riffs. But in a strange coincidence, Jurgen discovers that he shares his zooniversary with Carl the chameleon, who prefers a much quieter party to remember his arrival. Will either get the celebration they hope for?