Stan Lee rocks an amazing set of Fantastic Four pajamas when Penny and Leonard come to visit him at his home unannounced.
When Leonard goes to surprise Penny with a trip to Switzerland, he makes her a plate of Swiss hints.
On the 3/1/10 episode of The Big Bang Theory, Sheldon ends up in jail. Don't worry. He'll get bailed out.
This photo is taken from "The Einstein Approximation." During the half hour, Sheldon continues to search for the answer to a physics problem.
After some security concerns after a break in, Sheldon finds himself sneaking out on his ledge.
Penny and Leonard come outside to see Sheldon trapped by a net from the security system they installed.
When Sheldon and Raj get a security system installed to combat intruders, it back fires on them.
When the boys' apartment gets broken into, they call upon Wolowitz to help them install a security system.

TBBT Quotes

Sheldon: I recently read that during World War Two, Joseph Stalin had a research program to create supersoldiers by having women impregnated by gorillas.
Howard: What a sick use of science.
Raj: Hey, as long as the baby's healthy.
Amy: I wonder if Stalin considered any other animals.
Leonard: Hippos are the deadliest creature. A half-human, half-hippo soldier would be pretty badass.
Howard: Yes, but when they're hungry-hungry, you can stop them with marbles.
Sheldon: Yeah, the correct animal for interspecies supersolider is koala. You would wind up with an army so cute it couldn't be attacked.

Raj: Well, to paraphrase Shakespeare: It's better to have loved and lost than to stay home every night and download increasingly shameful pornography.
Penny: Oh... you poor baby.
Raj: What's wrong with me, Penny?
Penny: Nothing, nothing. You know, if we weren't friends - and you hadn't brought up that creepy pornography story - I'd be on you like the speed of light squared on matter to make energy.
Raj: Hey, you totally got that right. E = MC squared.
Penny: I listen. I have no idea what it means, but I listen.