"Baby, What a Big Surprise" is a song written by Peter Cetera for the group Chicago and recorded for their album Chicago XI (1977), with Cetera singing lead vocals. The first single released from that album, it reached #4 on the U.S. Billboard Hot 100 chart.
Carl Wilson of The Beach Boys provided additional backing vocals on the recording.
Although Chicago XI yielded two more minor singles, "Baby, What a Big Surprise" was…
Right before my very eyes
I thought that you were only fakin' it
And like before my heart was takin' it