Mike is a companion of The Second Chaka. He grew up living in the Nether, until he met The Chaka. He helped The Chaka repair his TARDIS, battle monsters in The Nether, defeat Snowmen in Chaka City, and helped defeat The Master's Torchwood plan. Mike finally settled down in an apartment in Chaka City away from The Nether.
Mike first appeared in Chaka Who #2.2, where The Chaka broke into his Nether house.