Egg Wheel

The Egg Wheel is a vessel used by Doctor Eggman as he is being chased through the city sewers, during the Hunt for the Chaos Emeralds ; the android Gemerl notably acts as co-pilot for the Egg Wheel (as he did in "Sonic Advance 3," when the Egg Wheel was last used), his head sticking out of the front, which is the first clue that the Doctor has the android working for him once more.

The Doctor first surprises Tad with the sudden appearance of the Egg Wheel, which rolls very quickly after the frog as a chase ensues. GIR soon flies in and kicks the Egg Wheel from behind, but it simply rolls faster. Amy whacks Sonic toward the Egg Wheel with her hammer while he is in Spin Dash form, and the Egg Wheel is finally thrown off-course from the impact. Sonic chases the rolling Egg Wheel through various tunnels before leading it to a large chasm and kicking it downward, causing it to fall and explode, the blast decimating a city intersection above.