I searched but couldn't find the original cartoon, so I'll give as much as I can remember. From "Life In Hell" by Matt Groening.

16 Steps to Adulthood.

1 -First time you hear a dirty joke.

2 - First time you repeat a dirty joke.

3- First time you understand the joke.

4- First time you get into a serious fight.

5- First time you steal something

6- First time you have a car accident

7- First time you get a job

8- First time you get fired

9- First time you get drunk

10- First time you come home drunk

11- First time you're jealous of someone younger than you

12- First time you get something you're not going to 'grow into.'

13- First time you say 'when I was your age...'

14-First time you skip dessert

15- First time you skip Halloween

16- First time you say "Jeez, I'm not a kid anymore."