When Doug and Spence are talking on the couch, a pink book on the coffee table moves around between shots without them touching it.
There is already food around the baby's mouth before Carrie tries to feed him.
At Mr Kaplan's beach house, the 'brick terrace' audibly creaks as Doug and Carrie walk on it, revealing it's clearly made of something like plywood.
Even if Carrie returns the items to get her money back, she still buys all those dozens of expensive items which would break her credit line easily as she is not a big earner.
Doug looks at the credit card charges, and comments about not being "Mastercard's bitch". However, the papers clearly say Capitol One (which is normally Visa).
Doug says that Spence hasn't had a girlfriend in 5 years, yet 2 episodes prior he did.