Grunt with toys
From Halopedia, the Halo wiki
The Grunt playing with dolls is an easter egg that can be encountered in Halo 2.
During the opening cinematic of Delta Halo, at the very beginning were you see the Grunt, look closely at it and you will notice that he has a Master Chief doll and a Grunt doll in his hands. It is easier to see if you take a picture and zoom in with a editing program, or have a modded Xbox that lets you detach the camera then freeze time and look at the Grunt. If you have Halo 2 Vista, you can use the detachable cam.
On other Easy and Normal difficulties, the Grunt is playing with the dirt. On Heroic, the Grunt is playing with fire. The objects are replaced as the difficulty is raised.
The objects disappear shortly before the UNSC Human Entry Vehicles land.
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