Police were called to Gorleston after reports of someone dressed in an all-black bodysuit jumping out in front of cars.
The incident happened on Tuesday night in Pier Road near the Ocean Room at about 11.45pm.
Concerned members of the public alerted the police when they saw the shadow-like figure walking out in front of traffic.
It is believed the person was wearing a 'Morph Suit' – a popular fancy dress item that is made from Lycra material that covers the whole body and face.
A couple were so alarmed by incident that they approached a young woman walking alone to warn her about it, and escorted her home to make sure she was safe.
A spokesman for the police said they encouraged people not to jump out in front of cars.
If you witness anyone partaking in this behaviour, police have asked you call the non-emergency line 101.
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