Ooh, yes, we have obsessions here, too!
My oldest is now 6 and has been baseball-obsessed for years now. It's particularly noticeable now, as he knows more and notices more about baseball than 'most any adult would. He could easily sit and talk players, teams, ballparks, and play-by-plays with a seasoned adult aficionado. He pays close attention to when our home team is playing, where, and against whom (I did give him a calendar to keep on the fridge), and will ask questions like, tonight, "Mom, can you check and see if we swept the Cardinals tonight?" ... because he knows (and I don't!) that this was the third game of three and we won the first... And he can spend the Whole. Day. throwing and catching soft balls in the house. He was nearly in tears one day because I tried to tell him that at 6, he doesn't NEED to know how to throw a fastball, curveball, knuckleball, and slider. He'd seriously spent day after day throwing balls, "practicing my pitching," after reading in a DK book about baseball.
Anyhow, I adore baseball, but he's definitely obsessed!
Tomorrow he starts his first baseball summer camp. Last week when I told him it started Monday, he explained to his Grandma that he had to be there at 8:30, so he needed to leave at 8:15 and be ready by 8, so he'd have to get up at 7. (And while no one had previously discussed this with him, I hear it's the plan for tomorrow!)
So, he loves baseball... Though as someone else mentioned, when baseball isn't in season, he does get interested in other things, too, like Cars. Yup, the capital-C kind. I don't like "characters" and avoid them at most cost. Somehow we ended up with some of the Cars vehicles, anyway.
: They played with regular cars before that, but had quite a big Cars kick - both the 3yo and 5-6yo. Thankfully after what seems like ages that seems to be dying down a
bit.
When my middle DS was a toddler he would carry things around forever! There was a little plastic hippo we got from someone's birthday party goody bag, and he had it in his hand for a full two-week cross-country road trip! He was about 20m at the time.
My 8mo is obsessed with strings.
If there's a string, or a string-like object, he'll find it... and chew on it, of course.
But I dunno if that's "normal" 8mo behavior or particular to him.