Lower doses can induce hallucinations before it becomes full on delirium that you see in higher doses. You'll regularly hear about people seeing "spiders" after taking 25-50mg of Benedryl, the recommended dose.

I think that may be more common in the elderly. I had full-on delirium from 5 x 50 mg, however. I would not recommend. It took me months for my body to recover. The auditory hallucinations lasted the longest (2-3 days), but my body and my mind was a wreck for months. Thanks to our beautiful hospital that did not administer the antidote for anticholinergic toxicity.