When Snart is recruited by Barry, he is wearing his big coat with the fur hood. When he is returned to Siberia, he is wearing a different jacket with no hood.
Snart tells Barry that the reason the shark in "Jaws" is not seen very much is because they couldn't make it look good, but in fact, it's because the shark (known as "Bruce") experienced several mechanical problems, forcing the filmmakers to use it less than originally intended.
Barry manages to get himself and Snart into the ARGUS facility by knocking out a pair of armed guards. However in a heavily fortified building, a guard's function is not just to keep out undesirables, but also to *allow* entry to authorized personnel - which would therefore become impossible without the guard's active cooperation.
HR changes his appearance to look like his assistant to everyone outside of STAR labs. He is never shown to reveal his true face to Tracy, but when Harry arrives she first thinks he is HR. Harry should have been a stranger to her.