The I Am The One Who Knocks tee design is for Breaking Bad fans and to some extent The Big Bang Theory fans. However, if you are not a TBBT fan, seeing Sheldon get slapped silly might make this a great tee for you.
This concept for mash up stems from Walter White's line "I Am The One Who Knocks." and the fact that Doctor Sheldon Cooper is always obsessive compulsively knocking on people's doors three times and saying their name once then repeating these actions two more times. Usually on Penny's, Leonard's, or Amy's door. In this case Penny's. I'm not sure why Heisenberg is at Penny's apartment. So that story is anyone's guess. She did know a lot about meth labs in Nebraska.
As for the artwork, it is illustrated well enough that one could almost hear the knock across Sheldon's head. The shading and colors are top notch. Gotta love the motion lines. Only Walter's face is showing as Sheldon's back is to the viewer. It is easy to tell who it is supposed to be because of the hairstyle and the trademark tee shirt over a long sleeved undershirt.
This I Am The One Who Knocks tee would make a great gift for the fans of both franchises.
I wouldn't recommend it as a school garment with obvious violence and the Breaking Bad reference. Other than that, this will make a great cross fandom t-shirt for any casual occasion.