Star Trek

I must have a faulty memory circuit or something.  I seem to remember, from somewhere, that Gary Mitchell was Kirk's first officer until his death on Delta Vega, after which Spock started doing double-duty (later earning him a promotion from Lt Cdr to Cmdr between Seasons 1 and 2)...

But!  The problem is that in "Where No Man Has Gone Before" and "Enterprise: The First Adventure" (the novel where I thought I got the idea from) he's just the navigator.  Maybe it was from another book or comic that I've forgotten about.  Can anybody help me out--or did I just invent the whole thing in my head all by my lonesome?

Subcommander/Commander T'Pol of Enterprise NX-01
Lieutenant Commander (later Commander, and later Captain) Spock of the USS Enterprise and USSEnterprise-A
Commander William T. Riker of the USS Enterprise-D and the USS Enterprise-E
Major (later Colonel) Kira Nerys of Deep Space 9
Lieutenant Commander Worf of the USS Defiant
Commander Chakotay of the USS Voyager

The Starfleet of the alternate reality established in 2233 by the temporal incursion of the Romulan Nero had the following noteworthy first officers:

Lieutenant Commander George Kirk of the USS Kelvin
James T. Kirk, first officer of USS Enterprise (promoted by Captain Christopher Pike)
Commander Spock of the USS Enterprise

In the 1st DC Comics Annual from the 84-88 Series

There is a very different tale of Kirk's first mission as Captain of the Enterprise which includes the handover ceremony.

During this Gary get's a bleep on his communicator and the person at the other end tells him he has a message that reads "Get Your Tail here, you're my new First."