Robo Fizz
The main Robo Fizz we encounter in Helluva Boss is an animatronic performer at Mammon's theme park Loo Loo Land. Robo Fizz has been performing there for at least a decade as he's shown to have frightened Octavia as a small child. Blitz is also shown in this flashback indicating they once worked there together.
Most of Robo Fizz's interactions in Loo Loo Land are with Blitz in which he comes off as belligerent and confrontational. During their argument, it's foreshadowed that Blitz has a past with the real Fizzarolli.
At the end of the episode, Robo Fizz is eaten by a dragon from the Loo Loo Land petting zoo, and he doesn't show up again until season two with a cameo in Apology Tour. The show does, however, continue to show and reference Robo Fizzes throughout season one and two in advertisements and dialogue from other characters.
Notably, Fizz talks about Robo Fizz in Ozzie's in which he complains about the loss of Loo Loo Land Robo Fizz. During his rant, he indicates that this Robo Fizz brought in more income than the personal companion Robo Fizzes.
The next largest presence of Robo Fizzes is in Mammon's Magnificent Musical Mid-Season Special ft. Fizzarolli where we see a commercial showing many different models of Robo Fizzes as well as Mammon's own personal Robo Fizzes.
The season three trailer shows Robo Fizz will return in future episode(s), most likely as an antagonist.
Kitty
Kitty is a Robo Fizz model owned by Valentino in Hazbin Hotel. They have no known gender, so fans refer to them with a variety of pronouns. They can be seen serving the Vees in season one of Hazbin Hotel. Kitty is silent and shown to be subservient and obedient.
In season two we see that Kitty has a battle mode or program when Valentino sics them on Husk and Cherri. The addition of roller skates sets their fighting style apart from Loo Loo Land Robo Fizz's.
Trivia:
Robo Fizz's design was first revealed during the BLM stream.
His first appearance in the show was as a sketch in season one, episode one: Murder Family
When Helluva Boss was edited for its debut on Prime, the Fizzi Buddy advertisement was removed. The reason for this decision is unknown.