The Let Me Out tee design is for Rick and Morty and Mario fans. TINY RICK!
The concept is a hilarious mash up and parody of Nintendo's Classic Super Mario Bros. 3 video game and Cartoon Network's Rick and Morty Episode -Big Trouble In Little Sanchez (shown below). This is one of a few different versions of this concept by the same artist with varying text and layouts. Who wouldn't want to play a video game starring TINY RICK!?
As for the artwork, the coloring is crisp and vibrant, it works well on any color shirt. The shading is soft and is suitable for both franchises. This particular layout and version of this design is the one that more closely resembles the actual Super Mario Bros 3 game cover art. The texts "The coolest, most popular !@#$%&* KID in school yet!", "Wubby (Let me Out) Lubby Doob Doob", (Let Me Out) this is not a shirt" add plenty of show references to make any die hard fan happy.
While this is the Super Mario Bros. pose it is definitely more of a Rick and Morty fan tee.