7 Reasons Why You Should Watch One-Punch Man
5. The References
First, there are references to other anime. The most notable (and funny) is Puri-Puri-Prisoner's transformation into an angel, which is identical to Usagi Tsukino's own change into Sailor Moon. There are also characters who look like heroes from other series - Vaccine Man is reminiscent of Piccolo from Dragon Ball, for example. There are also others, more or less confirmed.
The series also mocks typical superhero movie motifs, like villains explaining their origin stories or plans in a couple of sentences or the superhero appearing out of thin air to save the day at the perfect moment. The cities which the superheroes defend actually have one letter names, because their sole purpose is to be either destroyed or defended.
More so, the series ridicules the effort it takes to be a superhero. Consider Saitama's ultimate secret to achieving amazing power: 100 push ups, 100 sit ups, 100 squats, and a 10 kilometer run every day. It may be impressive by human standards, but good luck if you think that sticking to this workout will give you superhuman strength!