How many pair of underwear can a 2 year old wear?

Ryker went through this phase recently where he had to wear multiple pair of underwear. He wore them all day long and he wore them to bed. At night I would try to take them off when he was sleeping and if he woke up to go the bathroom in the middle of the night he would realize they weren't all on and he would have a fit. Even taking one pair off because they were dirty was a project. He counted them as he pulled them on and he proudly showed everyone he could all the underwear he had on.