Doctor Gustav is known to be Kauff's arch-enemy. Despite the simple characteristic, he's a much more complex character than one might think at first glance.
Gustav was "born" on the 3rd of October 2009 as a result of a histerical brainstorming session between Andrei and Marius "Majus" Fietzek. While Majus formed most of the character's major traits, Andrei picked the name based on a close family friend.
It is rumored that the creators know the real reason for which Kauff and Gustav are arch-enemies and why they are so keen on being such a constant annoyance to each-other. However, they haven't disclosed it yet.
Gustav, also known as a "Monkeyologist", takes pleasure in taking over Kauff's show and questions from time to time. It is rumored that he has a son but nothing is known regarding a possible wife. His "trademark" pipe always makes an appearance, even though the first version of it got destroyed during the filming of Episode 6 from Season 1 of "Ask a Monkeyologist".
The Wig joke took shape after Gustav's first appearance, when Majus had to buy a bigger wig since the old one was very difficult to work with. Also, during the second season, Gustav's black mustache suffered a tragic accident and had to be replaced with a gray one.
The bow tie is a tiny reference to Doctor Who, a show which both creators are fond of and they constantly make references to it throughout the show.Something half-weird half-funny about Gustav is that, unconciously, Andrei helped Majus design the character based on a friend of his, called Augustin. This friend is the real-deal Psychotherapist. At the time of the design choices, nobody from SilverWolfPet caught on the resemblance.
Really, look! He even has the pipe! How could they have missed that?! Or the name??!
...the things you write when you open up a Wiki, heh!