Luke Skywalker is a Star Wars minifigure introduced in 1999.
Luke Skywalker started out with a bunch of yellow-toned variants in 1999 and other early years of the theme. While a lot of these featured different outfits (with such variety as those white robes he wore on Tattooine and those black robes he wore later on Tattooine), the main common features shared by his first variants were his head and his hairpiece. His hairpiece was a normal, tan male "wig", and his head was printed to look like he was either glaring or starting to fall asleep. Later yellow head variants (and later, flesh head variants) remedied this problem by raising his eyebrows, making him only look dead inside as opposed to prepared to go nighty-night.
Aside from the changing of the tone to flesh in 2004, the next major change to occur for Luke's minifig was a change of hairpiece to his Episode IV variant in 2007. Likely unsatisfied with the inaccuracy of his former hairpiece, LEGO instead decided to try one with shoulder-length golden locks and a part in the middle of the head. For some reason, they changed this again in 2011 using a new specially-moulded hairpiece, as if what LDD calls "Mini Wig, Girl" wasn't good enough.
Luke also got multiple heads featuring pupils in recent years, including bacta-tank, blast shield, smiling, upset, and cautiously-happy faces. In the 2014 LEGO Star Wars Advent Calendar (yes, brought to you by the same company that used to make sets like 706 Medium Basic Set (Canister)) LEGO decided to take a whole new direction with the Luke Skywalker minifigure, creating a special variant for an alternate universe where he remains a farmer for 30 more years.
Luke Skywalker makes his first appearance as an apprentice under Qui-Gon Jinn, during the events of Episode I. Oddly, for his appearances in these sets, LEGO changed his hair colour to brown and incorrectly labeled his minifigure as Obi-Wan Kenobi, who clearly is an old man with grey hair. At least they got the face right, though.
Luke Skywalker returns in Episode IV, starting out as a moisture farmer, literally about the most boring career imaginable, almost making one wonder if Star Wars is somewhat of a parody of the hero's journey. After buying some droids, losing one, and chasing it, he is saved by an old man, revealed to be Obi-Wan. After his aunt and uncle are killed by Stormtroopers, Luke journeys to become a jedi knight with Obi-Wan. On the way, however, Luke falls in love with his sister, Obi Wan dies, and Luke blows up a space station filled with bad guys.
After finding out his father was a jedi in Episode IV, Luke finds out his father is a sith in Episode V, and finds out his sister is a princess in Episode VI.