At a Borderlands 2 panel PAX Prime last month, Randy Pitchford teased attendees with an "accidental" glimpse of an easter egg paying homage to a super-successful indie game. Stop reading here if you don't want to get spoiled.
According to this thread on Reddit, there's a bit of Minecraft in Gearbox's hotly anticpated shooter. Screens from Borderlands 2 show a boxy customization option in the style of Mojang's hit game, along with some very familiar enemies, too. So it's in there somewhere. All you need to do is find it.