i think its actually quite a cute little tattoo, and like you said, it can be easily hidden and reminds you of your childhood (and something that you probably grew up with as well). i have a batman tattoo on my ankle, which people probably wouldnt see the appeal of and may think im weird for getting, but its something personal to me, and i also want an alice in wonderland tattoo next (with a pink elephant as well) the different elements that it will have mean quite a bit to me and im looking forward to getting it done. i agree that it probably doesnt appeal to everyone, neither would the harry potter one probably, and yes some people may see it as an odd thing to get, but as long as you are happy with it and have thought about it properly then get what you want.
it probably wont cost a lot (not sure on prices as it varies greatly with the different tattoo places) and probably half an hour to do at the most - though dont worry about getting it done, neither of mine have hurt, didnt even realise he'd done the 1st one as i built up the pain in my head, and the second one is quite a big one between my shoulder blades, took just over an hour to do and wasnt painful either, just pretty boring tbh, though its probably best to go with a friend if your nervous, they can help distract you then.