The hopper is an enemy in Jak II. It is a weak, small, hopping metal head only encountered in Mountain Temple and later in Haven City while escorting old Samos and young Samos to the transport balloon in the mission "Defend stadium".
Hoppers are small blue-skinned metal heads that closely resemble frogs. They have strong back legs, but weak front ones (albeit with claws).
The hopper lives on both land and in water, making it one of the few amphibian metal heads. They usually travel in swarms (although sometimes seen alone), which can reach up to twenty members. They commonly hide in water and will ambush prey, mainly by swarming them.
A hopper will jump up to enemies and strike them with its claws. They are extremely slow and easy to avoid.
A lone hopper is not worthy of firing any ammo at, just get rid of them using a melee attack. Aside from that, the Scatter Gun is a recommended weapon for its large radius; great against the big swarms you will encounter.