yes, it's interesting the way plants that don't really look alike can seem so similar when they're entangled in a bed and you're trying to make a reasonable rate of progress with the weeding. I don't have ground elder, and I'd find it hard to confuse buttercup with alpine strawberry, but I find buttercup amongst hardy geraniums can get lost. Another pair is enchanters nightshade and dog violet - even the the leaf bases are completely different, the colour, texture and level of matte-ness is sufficiently the same for it to be easy to pull up the wrong one. It's not until the enchanters nightshade has put on about 6 inches of vertical growth that it starts to look obvious.