You know, as much as I like comics such as Scooby-Doo Team-Up, I do believe Scooby was best represented by the Marvel title, which did some great stories, such as as this one:

I just noticed - look at what they're all chanting in the first panel - "Big dog! Big dog! Bow wow wow!".

That's a slight modification of Cole Porter's Yale University fight song: "Bulldog! Bulldog! Bow wow wow!". The song was featured in the movie "Night and Day" in 1946, so it would have been reasonably well known when this comic was written.

Yeah, until that ice cream gets to his stomach and colon.........

Well, if you believe Wikipedia, it is from Victorian pickpocket slang; but, the reference for that consists of a pair of websites and not any scholarly works.  A "kick" was supposed to be slang for a front pocket, safest from theft but that doesn't really explain "sidekick."

As a literary trope, it goes back to ancient literature, including Enkidu, in Gilgamesh, Patroclus to Achilles, in the Iliad, and characters like Sancho Panza to Don Qixote (or Little John to Robin Hood, or Will Scarlet, in some of the legends).  Usually, to be a real sidekick, you have to be the junior partner in the relationship, subordinate to the hero.  Where the partnership is more equally, the term sidekick becomes a false notion.  You could argue someone like Tonto, based on variations of depiction, as sometimes he follows the Lone Ranger's lead and other times he acts of his own volition.

With Tintin, I would say more companion than sidekick.

I always liked Porky Pig as a sidekick to Daffy Duck; but, then again, Daffy is the butt of the joke and Porky kind of acts as the observer and enabler of his shenanigans, proving to be the actual hero in their adventures....or mostly amused by them.

Tonto to the Lone Ranger is a good sidekick, if you want to label him as such, though I think they work better as equal partners.  Watson is a good one to Holmes, in the better interpretations of the material.  He exists as an observer for Holmes to explain his methodology, for the reader, which was a common function, in detective stories and similar.

Within comics, I think Robin was, at times, a great one and certainly the best of the junior assistants to superheroes.  That's why I always enjoyed seeing him come into his own, as a hero.  I liked the concept that, as an adult, he is one of the best superheroes out there, as he grew up in the role and has tons of experience, by the time he reaches adulthood, not to mention his previous circus acrobatic training.  He worked with and learned from the best, even more than Bruce Wayne did, in his journey.