Is my colleague's statement true that cats entering mosques are Muslim jinn, and that dogs do not enter mosques because they represent Satan?

The statement that a dog does not enter the mosque because it represents Satan is incorrect, both legally and practically. Dogs used to enter the Messenger of Allah's mosque, peace be upon him, in the beginning, and were then prevented later to honor the mosques and have doors placed on them. Furthermore, Satan enters the mosque and whispers to those praying.