What are these characters from?
Viewing post in Super Tilt Bro. for NES comments
Sinbad is the mascot of the Ogre3D graphics engine.
Kiki is the mascot of the Krita painting software.
Pepper is the main character of the webcomic Pepper&Carrot.
VGSage is the mascot of the VideoGameSage forum.
The first three are from the free and opensource culture. Based on Super Tilt Bro. being an opensource project.
The last one is from the retrogaming community, because this is a game for the NES.