Guinan, El-Aurian race, has only been on the Enterprise-D for a few years ("The Child"), and didn't know Picard before coming on board ("Time's Arrow") but somehow has known Picard for a long, long time ("Time's Arrow").

She is 700 years old (according to Richard Arnold at a 1993 Leicester UK Convention). Her relationship with Picard is more than family; more than friends (from "Best of Both Worlds II").

She was on Earth in the late 1800s ("Times Arrow"). This is her first time of meeting Picard (but not Picard's), while Picard knows the 24th Century's Guinan already.

Her race (or just her) is believed to have the ability of sensing beyond linear time, since she is the only one who notices something isn't right in the alternative timeline created in episode "Yesterday's Enterprise".

Guinan, Dr. Soran and 45 other passengers on El-Aurian refugee ship were rescued by Enterprise-B when the refugee ship was caught by Nexus ribbon on stardate 9715 (in year 2293) ("Star Trek: Generations").

She is left-handed (not surprising, since Whoopi Goldberg is).