In the episode "Her Boyfriend's Back", Mark puts out his
cigarette before he gets up from the couch to give Roseanne a message to give to Dan. As Mark is closing the door when Roseanne leaves, he has another cigarette in his hand.
In the first season, the front door doesn't have a dead bolt on it. Then in a few episodes in the middle of the first season, the front door has a dead bolt. Then later on, the dead bolt is gone and then reappears officially in season 2.