Ok, so I have a fan theory / headcanon about Riddler from the Batman Arkham games - I think that at some point between Arkham City and Arkham Knight, he became a dad. Here is my evidence, in order from least to most convincing (some minor spoilers included):
Riddler makes several references to children’s games, songs, and fables when Batman is completing the racing challenges (the wheels on the bus, the tortoise and the hare, and even Mario Kart - “don’t tell me I have to hover in front of you with a flag to get you to turn around!”)
In an effort to get Batman to focus on rescuing Catwoman, Riddler at one point promises him a banana if he goes to the next location - bribery is a very common tool used by new parents to get their kids to cooperate
Throughout the storyline involving Catwoman, Riddler is constantly forcing the two to work together (almost like he has experience dealing with small children who don’t always get along). At one point he actually refers to Batman and Catwoman as children
There is green graffiti all over Gotham, much of it splotchy like it was rushed - or like there was child participation. I’m also pretty sure I saw a few handprints, which, I mean, come on...
Several of Riddler's puzzles in Arkham Knight were familiar puzzle games - the kind you might see in a toy shop or at a carnival. Why would Ed have suddenly stopped coming up with his own puzzles? Maybe because he’s very busy entertaining a small child at home (or maybe these puzzles were some of the favorites of his little one)
His death robot at the end of the game looks an awful lot like Mr. Electric from Sharkboy & Lavagirl - could it be possible that he watched it with his child and took inspiration from there?
In the movie studios, he plays “Riddler Says” with Batman - another popular children’s game
He has now taken the time to make sure all of his riddles rhyme, so that they now sound like nursery rhymes - could it be that this was his child’s idea?
At the beginning of his side quest, he lays out a clear list of rules for Batman - just like the rules you would tell a child before babysitting them
Particularly, rules 7 and 8 - if you need to use the bathroom, you must hold it, and if you have an accident, it is not my fault - if that’s not an exhausted dad who’s had to deal with said accidents far too often, I don’t know what is
And finally, and most obviously, the Riddler’s choice of clothes in Arkham Knight is very reminiscent of a suburban dad - the Hawaiian shirt is a dead giveaway