Kellin (portrayed by Bill Mumy) was an enlisted Starfleet engineer who appeared in the Deep Space Nine episode, "The Siege of AR-558". He was assigned to tinkering with a Dominion communications array that his unit had captured five months previously. When Captain Sisko and his team arrived to reinforce the unit, Kellin quickly struck up a friendship with Ezri Dax and the two worked together to locate and reconfigure the Dominion's "Houdini" mines that had been placed around the compound.
When the Jem'Hadar made their assault against the camp, Kellin was killed when a Jem'Hadar soldier shot him in the back.