They are sort of retro, I remember I found them in Mom's wardrobe as I was little.
However the print of collar is jack russell terrier-- I have one named Jojo(!)--
So I just couldn't help grabbing it even after the trend seems to have disappeared.
shorts: Forever21(similar here)
detachable collar: Miu Miu(old)
bag:Jimmy Choo(similar here)
shoes: zara(similar here)