Intertextuality - Easter Eggs.

Intertextuality is recognising the connections of one story to the other. In terms of media a best way of describing intertexuality is simply one film/cartoon/etc. making a reference to something that their target audience may understand.

The simpsons is a great source and is full of intertextuality and references. 

Why? Because it is a family show, and they use many different references for all kinds of people to laugh at.

However

Intertextuality must not be used if it destroys the general point as a whole. The plot must still make sense to those that don't understand the reference and it is simply a little 'easter egg' for those that do.

Easter Eggs in video games:

Easter Eggs are part of a video game which are added bonus's to the player. These are not a fundamental part of the game and can reference anything from prequels of the game to the producers to even things completely unrelated to the game as a whole.

For example, in World of Warcraft, If you get the achievment "Shop Smart Shop Pet...Smart." you will recive a in-game companion skunk named Stinker. If you come across any cats while Stinker is out, he will chase after them with a heart above his head. This is a reference to a Looney Tunes character which many people born before the 90's will understand!

Another is in a  game called 'Runescape', Use any herring with any tree on RuneScape. You will get the message "This is not the mightiest tree in the forest." This is a reference to 'Monty Python and the Holy Grail', where the Knights' Who No Longer Say Ni demand "Find the mightiest tree in the forest and cut it down withA Herring!" 

As you may know, the two are completely unrelated to their references but the joke still stands without destroying the general plot.