Whoa. Define dag? lol! I suppose there are a few definitions, really, but the main one - & the one I always use it as - is this: Dags are considered amusing just by being themselves and attract feelings of endearment from others.

To clarify, you making Daleks out of who knows what, or giving the toy versions shower caps and brushes etc may seem silly to everyone else - but I personally think it's adorable and very -you-. Therefore, this is daggy behavior. A little silly to others perhaps, but amusing & endearing to me.

I really don't recall using the term in any other way. Oh, wait, no I lie. Another time I use it may be for dress sense (or lack thereof :P) eg: If I'm feeling daggy myself, that may mean a touch slovenly. ie: large T-shirt, sweat pants and slippers ;p But other than that lovely visual, a dag is the above :)