Most generally, anyone who has ever had an iguana in an enclosure that was too small has seen their iguana digging. Digging is a normal sign for a female iguana that is preparing a place to lay her eggs. Digging can also be just the action of a curious or mischievious iguana. But, it is usually a sign that it is not happy with its environment. If your iguana is constantly digging around in its habitat, it may be wise to make sure that the habitat provided is set up properly.
Chances are, there is a good reason for a constant digging behavior.
A charging iguana is a dangerous one. Anyone who has ever had an iguana charging at them will tell you that this is a very true statement. The signs are obvious and usually involve a large male iguana charging in attack mode. An adult male iguana is very capable of suddenly charging, and extreme caution should be taken if you suspect that your iguana is in breeding season. Basically, when an iguana charges at someone, it is due to breeding season aggression.