What the ABC's Todd Sampson asked the sperm donor who fathered 164 children

Mathematics professor Ari Nagle is the man in question and he says he's been responsible for 164 children. He's very responsible for some of them; five mothers have successfully sued him for child support.

Nagle is also in the lives of other members of his brood, attending birthday parties and organising get-togethers.

Todd Sampson follows Nagle around on his deliveries, which involve giving samples in public toilets and hotel bathrooms - places that don't reflect positively on what he's doing.

Sampson does indeed ask the question "why?" and I won't spoil it by giving you the answer. But it doesn't feel like Nagle's being entirely honest - either because he hasn't really thought about it too deeply or because he has and doesn't like what he found.

Ultimately it falls to Nagle's father to explain his son's motivation, which is a deep moment in what seems like a flippant subject.

Marc Fennell has come a long way from being "the Movie Guy" on Triple J.

Where he has ended up is as the face of some of the best documentaries and TV series in recent years.

His documentary film about the Western Sydney Wanderers Came Came From Nowhere was a cracker and delved deeply into the club.

There's also the excellent TV series Red Flag, Framed and The Mission - the last one about a very strange art heist.

His latest series looks back at another eye-popping time in Australian history, the growth of the National Safety Council of Australia in the 1980s.

At the helm was the mysterious John Friedrich, who saw that the group had an impressive array of planes, helicopters, ships and even a mini-submarine.

It had better equipment than even the Australian Defence Force, which raised obvious questions as to how Friedrich was paying for all this.

The answer is by fraud. On a massive scale. It was the 1980s, when banks seemed keen to throw money at anyone who seemed like a good bloke.

He ended up owing the banks $300 million, getting caught out using bogus equipment as security against the loans and falsifying financial records.

And John Friedrich wasn't even his real name, which caused embarrassment for the Department of Defence which had given him a security clearance.

Interviewing a range of safety council workers and journalists at the time, Fennell has pieced together a fascinating tale about a man who really shouldn't have been able to do what he actually did.

It's never a good look to have serial killers who are unknown to the public.

These are offenders who have killed large numbers of innocent people - a crime you'd normally expect people to remember.

Such a term clearly suggests America has so many serial killers that it's hard to keep track of all of them.

Especially one who some have suggested was the most prolific serial killer in American history.

Though that's dependent on whether you believe the killer in question - Carl Watts.

He was sentenced to life after confessing to 13 murders but later said he killed 40 people and then more than 80.

Killers aren't known for their honesty, but they do like big-noting themselves so it's entirely possible Watts was just making stuff up.

This is a pretty straightforward retelling of Watts' crimes, with a few interviews of witnesses and retired cops.

The makers obviously didn't have more than one photo of Watts; every time his name is mentioned they flash up the same grainy mugshot. And each time it's captioned with his name, as if we had forgotten from when they showed it a few minutes earlier.