Motobug in Sonic the Hedgehog 1 is a hack of the original Sonic 1 game, replacing Sonic with the Eggman ladybug robot. When the original Sonic 1 game begins, Sonic encounters the motobug at the beginning of the first level. That may be a reason why the motobug is being used in this hack. The motobug travels through each level very slowly, but there are a lot of power snickers monitors in some levels, which makes it travel as fast as Sonic, so can complete a level. Some of the levels, motobug cannot complete, its impossible. This is due to the lack of power snickers monitors. If you are to play as motobug in other levels, the level select cheat will have to be activated. This hack isn't the most addictive, due to motobugs inability to complete some levels. But the sounds and music remain the same, as does the zone layout. The special stages remain in this hack, so motobug can compete in those. But motobug's slow movement and the lack of power snickers monitors means the game cannot be completed in full, it may require skipping between levels by activating the level select cheat.

Some levels are not complete-able because this is still in a beta stage. I don't know when the game will be completed (or if it even will be) but it is a funny game all the same. 
 
 -EDIT-  small typo