When you see people from your past, you start acting like you did when you used to spend time with them. (i.e. you start acting like a 14-year-old when you unexpectedly run into your freshman year boyfriend at the grocery store)
When Linda, the 50-year old elegant socialite, would squeal with delight, bounce on her heels and speak in 70's youth-vernacular whenever she got together with her sorority sister Patty. Her husband explained to his friend, "It's just Revertigo."
A baby that is conceived during a rocky period in a marriage, when it is hoped that a baby will (even temporarily) bring the couple back together. Usually the wife plans this baby behind her husband's back and pretends to be surprised.
Lisa: I thought Rick & Joan were heading towards divorce?
Brenda: Yeah, but then Joan announced her pregnancy.
Lisa: Ooh, band-aid baby. She is too meticulous to "forget" to take her birth control.