In "Be Mine", Beast Boy sings the song Fade Away by...himself.
Adored by the Network: Once the show was on the verge of premiering, CN advertised the show like crazy despite the fact that it was only meant for DC Nation. So much so that the show was even given a primetime slot on Tuesdays along with it's DC Nation spot. Beware the Batman, the other show on DC Nation, could only dream of such publicity...
Not to mention the three other encore slots that it started off with, plus the SpongeBob-esque schedule creep that started about three months after the premiere...
On October 26, DC Nation became 100% Teen Titans Go!, due to Beware being pulled from the schedule, before the block disappeared entirely.
"Pie Bros" is pretty much like "Employee of the Month" except no alien tofu, Beast Boy wants to buy something, and the plot is mashed up with elements from "Mother Mae-Eye" (including the eponymous villain).
The ending of "Legendary Sandwich" bears a lot of resemblance to Princess Bubblegum's story in the first "Five Short Graybles" episode of Adventure Time. Both stories involve the characters going to painstaking lengths to create the perfect sandwich only for it to be chewed up and spat out by someone who didn't appreciate it. It's funny, considering that Princess Bubblegum and Starfire share a voice actress.
"Terra-ized" was Judas Contract (and therefore the arc of season 2 of the original series) in a nutshell.
"Colors of Raven" uses the "different color Ravens for each piece of her personality" plot from "Nevermore".
The characters went through several◊ designs◊ before settling on their current ones.
In "Laundry Day" when Raven and Robin's suits were dancing, Robin's suit was originally going to be thrusting in the other direction, towards Raven's suit. They flipped the Robin suit's model to make it less suggestive. Though it still is pretty suggestive, considering what Raven's suit is doing...