As usual, crew members faced some unexpected challenges during the mission.

I had been a particularly awkward and unexpected challenge for him.

Q. What has been the most unexpected challenge in trying to develop the magazine?

It turns out to be an unexpected challenge, full of new friends and mysterious dangers.

She waited at the table for Logan to seat her, but when he did, it was with an unexpected challenge.

Critics say such unexpected challenges are the rule in nature.

Yet their marriage has been filled with unexpected challenges.

When new or unexpected challenges presented themselves, solutions were found using current military systems.

In fact, bun-splitting proved to be only one of many unexpected challenges for me.