A gang of youths were spotted pelting eggs at cars in Ossett on Halloween evening.
The group, of around 10 to 15 youngsters, were reported to police after being seen throwing eggs at traffic in the Church Street area of the town between 5pm and 7pm last night.
A mother who was driving a car with her child in the back was among those affected by the anti-social behaviour.
An object, believed to be an egg, struck the rear windscreen, close to her son.
Luckily, the boy escaped without injury and the car was not damaged.
But officers from the Wakefield West Neighbourhood Policing Team have launched an appeal for CCTV, after receiving several reports of objects being thrown at cars.
Inspector Helen Brear said: “We are looking into recent reports of youths throwing items at passing cars in the Church Street area and are appealing for information.
“Those responsible have clearly been behaving in a very stupid and dangerous fashion. While they may think they have been having fun, they have caused real distress to their victims and could easily have caused serious injury.
“Local officers attended in the town centre last night following additional reports and have taken specific action against a number of youths involved.
“They also remained on visible patrol in the Church Street area to deter further occurrences.”
Officers are urging residents to come forward if they have video footage or CCTV of the anti-social behaviour incidents or information about those who are responsible.
Details can be given by calling 101, emailing firstname.lastname@example.org or contacting Crimestoppers charity anonymously on 0800 555 111.