My boy loves trucks. My boy LOVES trucks.
He discovered his first car at around age 9 months, lurking in the bottom of the toy bins. We had some because I was an equal opportunity parent, girls can like cars too, except they didn't. My girls never touched the five or six small cars we had lying around the house. But when the boy showed interest, they tried to claim them: "That's my car!" And I quickly told them no, it's his, because he's the one who cares about it.
Fast forward two years, and he is patiently trying to explain to me as we head to the library that he needs books about trucks. So I ask the librarian, who guids us to the easy reading non-fiction selection, where there are short books about every type of truck you can imagine. Bucket trucks, skid steer loaders, snow plows, cranes, earth movers, etc. And our life has never been the same.
First, we never go to the library without checking out at least five books on trucks. Second, when we read one book about trucks, we read all of them. And third, we now know a lot about trucks. A lot.
Booms, dippers, tracks, wheels, front-loader, we've just all learned a lot about trucks.
When we are out in the car, when we see trucks, the boy will identify them for us.
Except he can't always use the "k" sound. If a word starts with "k" then he'll replace it with "t" (like "o-tay." But often in the middle of the word, he just leaves the sound out. (He can use it at the end of the word though, for words like "truck".)
So he shouts things like "look! that truck does have a bu-ut!" I try not to smile every time.
(And at least one of my girls has learned to play with trucks.)