Jump out of one's skin
To be extremely surprised or startled.

Caught off guard
To be surprised by something unexpected.

Throw a curveball
To surprise someone with something unexpected.

Out of the blue
Something that happens unexpectedly.

Take by surprise
To surprise someone without warning.

Bite the bullet
To face a difficult or surprising situation with courage.

Come out of left field
To be unexpected or surprising.

Throw someone a surprise party
To plan a surprise party for someone.

Take aback
To be surprised or shocked by something.

Steal someone's thunder
To take attention or praise away from someone unexpectedly.

A bolt from the blue
A sudden and unexpected event.

Hit someone like a ton of bricks
To be shocked or surprised severely.

Not see it coming
To be surprised because something was unexpected.

Have a pleasant surprise
To be happily surprised by something good.

Come as a shock
To be very surprising or shocking.

A surprise twist
An unexpected change in a situation or story.

Drop a bombshell
To announce something surprising or shocking.

In for a surprise
To be unprepared for something unexpected.

Come as a revelation
To be a surprising realization or discovery.

Take someone by storm
To impress or surprise someone greatly.