Yani is a minor villain in Dexter's Laboratory. He has only appeared in "Trapped with a Vengeance". He is the janitor of Dexter's school. He and his wife seem to be of Russian/Swedish origin due to his stereotypical Swedish accent and overall shape and features.
Due to Dee Dee being a constant nuisance to Dexter at home, Dexter prefers to do his experiments at school where it's quiet. However, he often overstays his welcome and leaves school at a very late hour, along with leaving an immense mess which Yani must clean up.
This causes Yani much misfortune, as working until late night causes him to arrive home at a late hour, which in turn causes him to accidentally wake his wife and she proceeds to unleash her fury on him. Having grown tired of Dexter's constant unintentional torment, he decides to trap Dexter in the school so he won't make it home on time to save his Laboratory from a laser wielding Dee Dee, which Yani was unaware about. Yani also fell for the fire alarm part so that Dexter could crawl through the vault. Luckily, his plan was broken by Yani's wife, with her finding him in the building, causing Yani to surrender and never trap Dexter with a vengeance ever again.
- He is voiced by Tom Kenny, who voiced the Mayor of Townsville in another Cartoon Network show, The Powerpuff Girls.
- He is referred to onscreen as Yani, but is only credited as Janitor.
- It is unknown what happened with him after "Trapped with a Vengeance", because he does not appear in other episodes despite being the school janitor. Theories that exist suggests that Yani was fired and arrested by committing several crimes in this episode: Kidnapping Dexter trapping him in Huber Elementary School against his will, and physical battery against a child to attack and punch Dexter.