To be misled about the purpose of a advertisment, commercial or conversation until the very end.
Derived from the Geico Insurance commercial campaign with the endings "...but there's good news, I just save a bunch of money on my car insurance."
Narrator: " It is here that many a salmon's life is cut short, but there is good news...I just save a bunch of money on my car insurance by switching to Geico."
Audience: AWWWW!! We've been geicoed!