For live action, Vaughn Armstrong holds the record.
I always wondered what he could have done with a TOS role, since that's the only Trek time period he's never done (he was in his teens at the time - although many other Trek 'repeat offenders', such as Phil Morris*, have done TOS as children). They should have given him a spot in ST XI. If there's a XII, they should look him up. Also since he's never done a Trek *film*, only TV series.
*Morris' Trek roles:
- TOS "Miri" (boy in Army helmet)
- VOY "One Small Step" (Lt. John Kelly, Mars astronaut)
- ST II:TWOK (Cadet Foster - the guy who wanted a celebration for the crew)
- DS9 "Rocks and Shoals" (a Jem'Hadar)
- DS9 "Looking for Par'Mach..." (a Klingon)
R&S- he was Remata'klan, therefore awesome...
