Being fluent in six languages makes Tim a very valuable member of the crew. Originally serving under Captain Stark, he continued his service under both Captain Bridger and Captain Hudson. When once asked if he could read a very ancient language, Temecuan, he replied with, "I'm not that dull am I?"
Tim was a friendly, but shy man, with an inquisitive nature. A quick problem solver, he would tend to get very nervous, and sometimes felt that he got pushed around and not appreciated. An avid Catholic, he often prays when in tight situations, prompting other crew members to ask if he'll offer a prayer for them too. He briefly showed signs of being slightly tele-empathic during Season 1 when Darwin became sick.
One of O'Neill's quirky peculiarities was organizing his underwear by the day. He, along with a
lot of other males, was strongly attracted to Ensign Lonnie Henderson when she first came on
board. He dated her, but decided he did not want a ship-board romance.