In the mid to late 90s, a Snap was a certain type of insult told in a specific format..."Yo mama" jokes, basically, which would often result in the phrase "Oh SNAP!" being yelled out when a given insult hit particularly hard.
For example...
"Yo mama so fat, when she tried to weight herself, the scale said “one at a time please.”
"Yo mama so old, she remembers when the Grand Canyon was just a ditch!"
"You're so dumb, you sold you house for rent money" "...Oh, SNAP!"
A young pilot who's made the mistake of showing feelings.
The new guy doesn't take instruction very well. He can't fly to save his own life and every time you try to give him some advice, he thinks he already knows everything and he starts crying.