If you've never seen the Regular Show before, you probably won't get the joke...
Just a little parody (which is protected by Section 30A of the Copyright, Designs and Patents Act 1988 as of 1 October 2014) based off the TV series, Regular Show created by J. G. Quintel.
The characters and references are the property of their respective owners, this (as mentioned before) is merely a parody for entertainment purposes.