Deadpan Snarker: At least according to the background information that Gene Roddenberry wrote for the character's species. He described the race as having an extremely developed sense of humor with a delivery so dry that they seem very cold and aloof to outsiders. Most other races don't ever realize when a Deltan is making fun of them, which probably explains the Breathless Non Sequitur she delvers to Kirk:
Ilia: My oath of celibacy is on record, Captain.
Informed Attractiveness: Your mileage may vary, obviously, but Ilia is one of a select group of Trek characters with less hair than Picard. Nonetheless several male crew members get all goofy around her. The novelization explains this as her race releasing pheromones whenever they're around unfamiliar males - so it's not really because of her attractiveness sometimes; they just can't help their reactions.