Tee-hee

Tee-hees are green ghosts who reside Mad Monster Mansion, chasing Banjo and Kazooie when they get close.

Banjo-Kazooie
In Banjo-Kazooie, Tee-Hees are found throughout most places of Mad Monster Mansion and near the world's entrance in Gruntilda's Lair. While invulnerable to most attacks, they can be defeated with the Wonderwing move.

A purple Tee-Hee also appears during Tumblar's mini-game, where it flies around the board counter-clockwise rather than actively chasing the duo. This enemy's role is to make it harder for the pair to be able to spell "BANJOKAZOOIE" in the tiles. If attacked by the Wonderwing move, the purple Tee-Hee is briefly defeated and drops a Honeycomb but immediately reappears and goes back to circulating the shed, making it mostly worthless to be attacked.

Banjo-Kazooie: Nuts & Bolts
In Banjo-Kazooie: Nuts & Bolts, various portraits of Tee-Hees can be found in many different places of Banjoland.

Trivia

 * The model for the Tee-hees' heads was reused from the trolls planned to appear in Dream: Land of Giants.
 * Mum-Mums, Limbos Tee-hees are the only enemies in Banjo-Kazooie that can only be defeated with the Wonderwing move.