The safeguarding of Earth and other worlds from biological cross-contamination (i.e. billionaires with too much time on their hands).

Also known as “planetary protection.” Planetary protection / quarantine “reflects both the unknown nature of the space environment and the desire of the scientific community to preserve the pristine nature of celestial bodies until they can be studied in detail.”

There are two types of interplanetary contamination. Forward contamination is the transfer of viable organisms from Earth to another celestial body. Back contamination is the transfer of extraterrestrial organisms, if such exist, back to the Earth's biosphere.

Inquiring as to the identity of a certain person in attendance at a party, in the club, or within the general vicinity of the speaker.

Who is that? aka...a cultural thang...none of the NFL's friggin' business!

A long time ago, people used to be embarrased when they had tickets to a Saints(LA football team) game. They would put paper bags over their head bc the Saints, honestly, were not very good players (besides Archie Manning).
Now, please understand, the Cajuns in Louisiana,(desendants from French, Spanish, and German colonists+Native americans in the area), had very thick accents.Sometimes, and I mean most older Cajuns have this accent, pronounce "this" as "dis" or "that" as "dat".
So the people would point at the fans paper bags and ask, "Who dat?"
There is also a singer that wrote a song with these words as lyrics a while back. In late 2009, a man by the name of Cracka Trax Ft. Dat Boi Pantha sings the song "Who Dat Say Dey Gonna Beat Dem Saints (Put The Hurt On 'Em)".He on the other hand was a Saints fan bc of how they played that season.They eventually went to the Super Bowl of 2010...Wait...We're all caught up now!I hope dey win!!!