Sid and Elvis are a pair of monkeys, the Jungle King's most loyal servants, who would do anything it takes to stop the kids reaching the temple. They even make some challenges harder, especially the Dark Swamp challenges, since they seem to like hanging around nearby the swamp.
On rare occasions, Sid and Elvis would kidnap one member of the team and place them in a cage where they would be discovered by the rest of the team and must be rescued. If they failed to rescue the team member, they would sacrifice a monkey statue. Rare kidnappings include the entire team being locked in a bamboo cage high up in the trees and must escape - again if the team failed in their attempt they would each sacrifice a monkey.
At the end of each show, the monkeys lounge around outside the temple of the Jungle King, and without fail Underwood tells them to "clear off". They obey him in a most obedient fashion. They follow the orders of the Jungle King, and they do lots of stuff to stop the jungle explorers, for example, they yank the ropes which control the baskets movement upwards while people jump (or swing) for them. They always disobey the Jungle Guide's commands.
Sid and Elvis have changed colour throughout the series of Jungle Run. In series one Sid was Red and Elvis was Blue and in Series 2 Sid changed from Red to Yellow while Elvis changed from Blue to Orange. In Series 3 Sid changed to Black while Elvis remained Orange.
In earlier Shows both Sid and Elvis had tails but during a show Elvis's tail came off! In later Series the tails were removed from the Monkeys.