LORELAI: You’re all acting like I walked into that room tossing condoms in the air.
LOIS: You might as well have.
LORELAI: Fine, next time I will. I’ll bring a banana and we’ll have a little show and tell.
Show and tell, also called show and share, or sharing time, is a common classroom activity in elementary school or primary school in North America, the UK, New Zealand, and Australia. Typically, a child will bring an item from home to discuss it.
Lorelai refers to sex education classes where teenagers are taught about safe sex by learning to put condoms on a banana.
The Annotated Gilmore Girls 