ROSES VS. VIOLETS
Rooster Teeth's "Red vs. Blue" series owes everything to Halo, but 343 Industries, like Bungie before them, are not above giving back. The fifth mission of the first Spartan Ops episode ("the Cauldron") features a sneaky little easter egg that involves shooting a small radio to hear dialogue from "Red vs. Blue" characters and the machinima show's iconic theme song.
The radio can be spotted by players who look over the barrier just before they reach the ramp. And we've heard there are more throughout the level, though we've yet to find any of them.