My cat lost his voice and drooling

About 2 weeks I got a kitten, mainly for Mikko to have a friend.

He is not taking it well. He is eating and drinking but I noticed he lost his voice, drooling and has a funny smell now, almost like he stopped cleaning himself.

A checkup by the vet would be advisable - the kitten could have infected Mikko with an illness. Even if it didn't, drooling and hoarseness are worrisome, as is the smell. He may have some sort of infection which will just get worse without proper treatment.

A lost voice and drooling signals a possible airway problem, which is a veterinary emergency.  I wouldn't even bother calling your vet first, I'd just show up with the cat.  Please let us know how he is.