Roberto Benigni accepted his Oscars for Life Is Beautiful (for Best Foreign Language Film and Best Actor) as only he could: walking on the tops of the audience chairs to the stage and remarking there, "This is a terrible mistake, because I used up on all my English!"
The following year, when Roberto presented the Oscar for Best Actress in a Leading Role, Billy Crystal could not resist a great gag to followup: standing behind the star with a large butterfly net to restrain him if he gets so frisky again.
The 1992 ceremony included a small unplanned speech from a 100-year-old Hal Roach, but the man's words were unheard by the audience. Luckily, Billy Crystal made a joke on the spot saying that it was because Roach started out in silent films.
When Tom Hanks won his second Best Actor award for Forrest Gump, he makes a Call Back to the film by saying "So I went to the Oscars again, and I got the award again."
The 2010 ceremony had the "stars" of the five nominees for the Best Animated Feature award taking interviews. Even better, they're voiced by their original actors and animated in their movies' respective styles.
Then, there's the order for "A Lot of Pizza". The delivery man thought that the pizza is for the writers of the ceremony until Ellen brings him to the stage with her and passes out slices to the audience.