Klaus is very protective about anything related to his daughter. At times, he is frustrated by her constant habit of picking up stray pets but he often lets it slide as he is just as compassionate as his daughter for animals. He befriended a white tiger cub in episode 14. He is accepting of the fact that Roxy is a fairy.
Klaus either has a bad memory (possible from the memory spell put on him by the Wizards of the Black Circle) or simply has a playful nature as he called the specialists: "Smile", "Brandi", "Rivet" "Booboo" and "Tobias", it is debated whether or not this was a side effect of the memory charm placed on him by the wizards or if he was simply teasing them. One should also note that he remembered "Jimmy's Name" which he introduced himself as, and did remember the Specialist's names later on in the series.
In Winx ClubEdit
Klaus makes his first appearance in Season Four, Episode 4 "Love & Pet" as the owner of the Frutti Music Bar. He appears as a single father, raising his daughter Roxy as one of his employees. His bar is very popular with Andy's band performing every once in a while and fancy styles to make it lively and fun. Kind and generous he decides to hire the Specialists as his new employees thanks to their talents, looks and desperate need for a job! It also appears that he hired the Winx girls as well, but this is left un-specified due to their work with Love & Pet. He allows Musa to perform as well.
When Roxy tries to reveal to her father that she is a fairy, Klaus at first suggests she is joking; but it is revealed he is Duman in disguise. The Winx discover the real Klaus captured at the docks and confused as to what is happening. After a brief battle, he witnesses Artu becoming injured, forcing his daughter into a fairy transformation. Even more confused at this point with his daughter being a fairy, Klaus soon accepts his daughter for the way she is.
Through the rest of the season, Klaus is shown being reluctant to allowing Roxy to travel with the Winx in fear she may truly get hurt, but ends up allowing it. He is also aware of Riven's rocky relationship with Musa, and attempts to help him take his mind off of it by reminding him to do his job. Despite this, he truly cares about the Specialists like his own sons.
At the end of the Season, it is revealed that Roxy is Queen Morgana's daughter, and the latter is therefore the wife of Klaus. It is revealed the two had married long ago and had Roxy together while Morgana stayed on Earth as a human. However, when Morgana was forced to leave Gardenia to return to protect her Kingdom, she was sealed by the Wizards in Tir Nan Og, and all memories of her were wiped from the minds of all friends and family members as a result of the Wizards' negative magic, and Klaus was left to raise Roxy on his own. In the last episode, Morgana returns Klaus's memories and the two reunite; making their family complete with Roxy.
On Sora's TeamEdit
Like his wife Morgana, he has also recieved one the gems and can check on Roxy when he needs to. He can always overeact to the missions Roxy goes on with Sora, and Riku, and when she fights agains enemies like Young Xehanort, and Pete.