Mario and Luigi Bowsers Inside Story Easter Eggs

When you go to Plack Beach, find a tooth monster and knock it till its head is on the floor; it will then let a blue bug from its teeth. The blue bug is a Virus from Dr. Mario

When Mario was kidnapped by Sockops in Dimble Woods, and Luigi tries to rescue him, Luigi gets eaten too! Hop along the trail as Luigi in the sock and the blue and yellow spikes will not hurt you. When you find Mario, the Sockops are arguing over who... more

Once Mario and Luigi have learned to tunnel underground, have them speak to a toad just outside of Peach's Castle. He will teach you how to use the move to find beans. At the end of his tutorial, he will tell you that "It's a secret to everybody!"
This... more

If you go into the hospital and go all the way to the right, you will find a poster of a blue virus from Dr. Mario.

In peach's castle, after you have defeated snow midbus, find dark fawful while he is searching for the dark star in the conference room from the begining of the game. The device he is holding to track down the dark star is a Nintendo DS.

The first time you go to bowser's castle do what you are supposed to do until the door opens when it does open go in and walk to the back right corner. thats how you find one of them there are three more under the castle. but you need Mario and Luigi.