Start with a rap song about dark matter:
Now you're in the mood to enjoy scientific arguments regarding dark matter. Is dark matter only an idea? Or is it a real thing? First observations by Fritz Zwicky and later observations by Vera Rubin established the idea that there is something out in the universe which we cannot see but causes gravitational impact. Nice quote at 7m48s: So in the beginning you have the big bang. Lawrence Krauss has got an opinion about which stories should beginn with those words. Maybe we'll come back to this another day. Meanwhile dive into the evidence which leads to the postulate of dark matter. Bonus: at the end (41m32s) there is a crackpot compass presented.