Who was the alien who travelled with the crew on their adventure " Star Trek"?

Which Star Trek? Are you thinking of Warf/Next Generation?

Spock if talking about the original series played by Leonard Nemoy.


And no one should ever think of Next Gen or Enterprise because they suck :P

There were so many... which Star Trek are you talking about?

Spock- The Original Series
Worf- The Next Generation
Phlox and T'Pol- Enterprise
Odo, Dax, Quark, Major Kira- Deep Space Nine
Neelix and Tuvok- Voyagers


Of course, if you're talking about the Star Trek movies, then:

Lieutenant Ilia, Star Trek: The Motion Picture
Lieutenant Saavik, Star Trek II: The Wrath Of Khan, Star Trek III: The Search For Spock

Plus others I'm sure I'm forgetting...

Well, on The Next Generation, an alien that travelled with the crew that was not actually part of the Starfleet crew was Guinan the bartender (Whoopi Goldberg).