My bank is pretty picky about checks. My grandmother once wrote a check for my daughter's birthday. Sweet, right? Problem was that my daughter was 3 at the time. She had no account in her name. We didn't *want* one in her name. My bank? Would not accept a check that was signed by her parent (me) to put into my account. I could sign it if it went into *her* account, but I could not sign it and put it into mine. I ended up having to talk to customer service at my old bank, which I rarely use but still maintain an account with, and they were willing to accept the check from my signing it as long as I included documentation that I was her parent (I think they needed a copy of her birth certificate or something). I *think* either bank would have taken it if I'd been able to go in in person, but we're military and move around a lot and both banks were in other states. It was a huge pain, and much as I hated to do it because I worried it would make her feel bad, I asked my grandmother if she could write future checks out to myself and I would give my daughter the cash. Fortunately, she was fine with it.
I also sigh when I get a check that says "<PenguinHusband> and <MommyPenguin>," because my bank requires both of us to sign in those circumstances. If it says "<PenguinHusband> or <MommyPenguin>," they're fine with one signature from just one of us. I do have a PoA for my husband, so I can sign in his place when I need to, but then I need to include/file documentation showing that I have PoA and all that and it complicates things.