Usavich

They use very similar kinds of jokes and humour in general. The soundtrack also uses classic music in moments of despair a lot. The art is very simple sometimes in KLK, and so in Usavich. Crazy characters appear a lot in both (like Kirenenko and Mako). 

Both involve a duo's wacky adventure and don't have dialogues. They both make you laugh hard and are short 

They are almost identical in terms of humor and even characters. Same goes for the style and overall impression of weirdness.  

Both of them with Russian characters. Short stories. I think they have something in common. But Cheburashka is more for kids because Usavich has more specific humor. 

Very similar series. Short and humorous stories, 3D animation, somehow crazy (or even twisted) jokes, no voices - only music and various sound effects. 

A small package of senseless but fun animation, made of original joke with some historical references