Rottweiler

The rottweilis is featured on 'the spaghetti catalyst' in which Sheldon tries to remain friends with Penny and Leonard secretly after they broke up. Sheldon sneaks out of his flat to get some sausages for Penny to put in the spaghetti she was making, like how his mother used to make it. He bought some and hid the packet of sausages down his trousers so that Leonard wouldn't see but an angry dog that looks like a rottweiler follows him and barks at him. Sheldon is afraid of dogs and the dog senses he has food so sheldon gets chased by the dog and appears at Penny's doorstep with only one sausage left.