Slipped

The spy slipped the secret code into the message, without anyone realizing it.

He slipped and used a curse word in front of his grandmother.

The secret plan was slipped into a confidential memo, without anyone noticing.

He slipped on the wet pavement and sprained his ankle.

He slipped on the banana peel and landed on his backside.

She slipped on the icy sidewalk and slid several feet before coming to a stop.

The bird slipped out of its cage and flew away.

He slipped a piece of paper into the envelope and sealed it shut.

The mouse slipped through the small crack in the wall.

The spy slipped past the guard and entered the building undetected.