For a while, Arnold Schwarzenegger and Sylvester Stallone seemed to have this running joke where they would make comedic references to each other in their respective films.
 
Some examples:

Demolition Man: Stallone is dumbfounded when he discovered that Arnold became president...

 
Last Action Hero: In a video store is a poster for Terminator Two starring...Sylvester Stallone!
 
Twins: Arnold compares his abs to those of Sly on a poster for Rambo III.

True Lies: While Arnie is blasting away bad guys his wife says "I married Rambo."

Stop, or my mom will shoot: The woman who play's Sly's mum say's to some guy "I'll be back" and as they are walking out Sly say's to the woman 'What are you the Terminator?'

 

Rocky Humour

There have been many light hearted spoofs released over the years in terms of music, videos and pictures. They are obviously not intended to be taken too seriously...

Sly Stallone Meets Rocky Balboa

Special effects are used to make Sly meet Rocky. 27mb compressed in RAR so WinRAR will be needed to unzip the file.
With  rapidshare:

Go to bottom of screen and click free, wait for the timer to go down then click to download the file

Spoof of Rocky's training

Spoof of Rocky's training methods with a guy training in various humorous places.

Animated Rocky advert

(4.5mb) Advert for drinks company Brisk with Rocky and Mickey at a boxing fight.

Theme From Rocky XIII Right Click and Save as

(3.4mb) Spoof from Weird Al Yankovic of the 'Eye of the Tiger' song mocking the amount of Rocky's that have been produced

Animated Rocky VI Spoof

Flash cartoon mocking the rumour that Rocky VI could be on its way

Stallone's Career Photo

A spoof of the Rocky poster mocking Sylvester Stallone's movie career