If you’re in The Big Bang Theory fandom, you’ve seen this shirt before. But I’m fairly sure many viewers unfamiliar with comics don’t understand the significance of this shirt. In the DC comics there are different lantern corps, the most common of which is the Green Lantern Corps (I’m sure even fans not well versed in comics will know Green Lantern.) Well, the Green Lantern Corps is only one of the lantern corps. The lantern corps have power rings that bestow powers on the wearer, who is chosen because they have certain ideals and attributes that that particular lantern corps values. The Green Lantern Corps values willpower, and thus the rings are powered on willpower and the weakness of the Green Lanterns is fear. There are several more lantern corps the Sinestro Corps (fear), the White Lantern Corps (life), the Red Lantern Corps (Rage), the Orange Lantern Corps (avarice), the Indigo Tribe (compassion), the Blue Lantern Corps (hope), and the Black Lantern Corps (death). Each lantern corps conducts itself differently and has its own unique oath. The Star Sapphire Corps represents love, and its oath is:
“For hearts long lost and full of fright
For those alone in blackest night
Accept our rings and join our fight
Love conquers all with violet light”
Notably, Sheldon wears his Star Sapphire shirt at the end of “The Gorilla Experiment”
and again when he has dinner with Penny in “The Spaghetti Catalyst”
Whether intentional or not, Sheldon’s Star Sapphire shirt gives these Shenny scenes a deeper romantic subtext.