To “catch the vapors” means to get wrapped up in someone else's hype. Thinking you are more popular or glamorous by association, expecting favors, money or connections just because you knew them before they were famous.
Biz Markie’s song (Or Snoop Dogg's cover) Vapors explains it rather well with the following verse
So in school on Nobel Street, I say "Can I be down, champ"
They said no and treated me like a wet food stamp
But now things switched without belief
"Yo, Biz, do you remember me from Nober Street, chief?
We used to be down back in the days"
It happens all the time and never ceases to amaze
Another note. When European countries criticized the United States regarding the “decreased role for the European allies” in the war on the “axis of evil” and conquest of Iraq. U.S. Secretary of State Colin Powell dismissed them as to having “caught the vapors”
So if you get really famous and successful and people who wouldn’t give you time of day are now your best friend… well, they caught the vapors.