Tom in a Sonic vessel, appears as an anthropomorphic hedgehog with blue fur and quills, yellow teeth (side effect of the vessel being made of VOID matter), is the scar on his mouth, and other stuff.

( @SomeSonicAndMarioFan fan/parody account)

Although not much is known about him, it is known that he tends to be grumpy, and seems to have great courage and determination.