Okay, I'm prepared to get stoned for expressing my opinion on the matter, but I find Winnie the Pooh et al emblazoned across adult nightwear rather disturbing.
It's difficult to articulate quite why I feel this but I think it's because the Disney versions (which I hate, compared to the original illustrations, but that's another thread ...) are very "baby-esque" and marketed, on the whole, to very young children. You see those images most of all on nursery bedding, on cot mobiles, on cuddly toys for toddlers and so on.
To therefore have it on an adult nightie feels ....... sinister ..... I suppose. These "innocent" images being place into an adult bed. Perhaps I am over-analysing it in an attempt to answer the question ??
Leaving that theory behind, and again, in my experience, I have also found that the women who wear such garb have usually (well, totally, to be truthful) adopted a rather pathetic, babyish persona, as in, "oh poor me, I'm all helpless" whilst fluttering their eyelashes and pretending to be "just" a "silly woman" so that she can be "looked after" by a "big strong man" and that blinking well annoys me.
Guess I should go and hide now ......