Time flies, especially when you own a dog. What started out as a teeny weeny little pup transforms into a big grown up pup (sometimes, huge pup) in the blink of an eye. Dog owners took to Twitter to show their then and now photos of their dogs when they are just a few weeks old, and what they look like now. It's a nice reminder to appreciate every moment you get with your furry babies, as they grow up at a truly alarming speed.