Spark plugs don't tend to be a cause of weird sounds, so that's not your problem.
As to the cause, it depends what kind of weird sound it was. Was it a crunch, or a graunch, or a whistle, or a squeal? What part of the engine was it coming from? Were there any other symptoms, like a lurch forward or something? Does it still turn over with the starter? Do you get my drift here? Y!A is not really an accurate forum to diagnose this kind of thing. Might pay to put it on a trailer and take it to a mechanic.
