My puppy's head looks lumpy. Is this normal for a growing puppy?

This could just be a normal formation of your dog skull. If it is not getting bigger, does not feel like it has fluid in it and there is no discharge I would recommend just measuring it once a day for about a week and seeing if it truly is getting bigger or not. If it is not it's likely a normal skull developing. If it is getting bigger then have your veterinarian take a look.

First, great pictures and highlighting of the lump! This appears to be a fluid-filled lump. Usually puppies get these when they bang their head on something and then fluid accumulated under the skin. However, I do worry about congenital defects that could cause accumulation of CNS fluid under the skin. If Thor is otherwise acting and looking normal, then either way, it's not an emergency. If he is acting weird, then best to have a veterinarian check him out. If it was just a bump, then the swelling will start going down within a couple of days. If it continues to grow, then it would be concerning enough to make an appointment with a vet. An easy way to detect growth or shrinking is to draw around the edge to the swelling with a magic marker. It will look silly, but it's really easy to tell if the border of the swelling has moved. I hope this helps.

If I’m understanding the location correctly, it could be normal. Some dogs have a pronounced occipital crest. Something like this though requires actually touching it and looking at it to know for sure so you should have her seen. I hope this helps and please feel free to post any additional questions.

There can be several causes of a lump like this, including a seroma or hematoma from hitting her head on something, an abscess or infection, an enlarged lymph node or salivary gland (if the lump is lower toward the jaw), a tumor or cyst, among a few others. Since some of these issues need veterinary care to resolve, I would recommend that Fifi get checked out by a vet. After physical examination, the vet may recommend a needle aspirate and microscopic exam or x-rays to see what the cause of the lump could be.

If it recently got bigger than you should have a vet take a look at the lump to determine the cause. She could have an infection, cyst, or a mass and your vet can do a needle aspirate to help diagnose and then determine if any treatment is needed.

My concern would be that the other dog may have bitten Hope on the head. Keep an eye on the swelling. If it is getting larger, if it starts to leak fluid, or if she isn't going back to a normal attitude when she wakes up from her nap, she needs to be examined by a vet right away as brain swelling could be fatal.

That's quite a lump! If it is growing rapidly or is painful, then Smoke should be seen by your veterinarian or at the nearest veterinary ER as soon as you can get him in. The same can be said if he is lethargic or unresponsive. If he is behaving normally and the lump is not bothering him, you can wait until tomorrow morning to have him seen by your vet.