The circus flashback itself is a reference to Dick Grayson, the original Robin in the DC comics. This is in line with a previous reference to the circus in the original Teen Titans series when Raven entered Robin's mind, suggesting that the Robin in the show is the DC Animated version of Grayson. It should be noted that the episode baits viewers who know this into predicting that Robin stopped relaxing after his parents were killed just like in the comics, only to reveal that it's because the animals kept stealing his stuff.
In "Laundry Day", one of Cyborg's bodies is shaped like one of the Voltron lions in leg mode.
When Beast Boy uses a vacuum to suck up Cyborg's soul, the music resembles the Ghostbusters theme.
Starfire's dress-making skills and the end result is a lot like what the character Giselle does for a hobby in Enchanted.
When the suits start attacking, Robin's and Raven's suits slack off and dance to It Takes Two by Rob Base.
At the start of "Ghostboy", Beast Boy pops out of Robin's closet as a Velociraptor using the Jurassic ParkT. rex's roar.
"La Larva Amor" has several during the milk mustache contest, such as Robin becoming Mario, Raven becoming Gandalf and Beast Boy becoming Chewbacca, complete with Bowcaster. Also, Cyborg resembles B.A. Baracus.
Of the many references to other DC characters in the series, perhaps the most potentially impactful on the story was Beast Boy finding a Green Lantern ring in the couch at the start of "La Larva de Amor". Of course, as he was looking for something else, he tossed it aside.
Apparently the skeleton reaching for water under Starfire's bed was Deadman (Boston Brand).
He mentions that the actor who played Webster "was like 40 in real life". Cyborg may have confused him with Gary Coleman, who starred in Different Strokes.
When Cyborg is hooked up to the Titans Tower mainframe, he loses his humanity and starts acting more like HAL 9000. He even starts speaking in a Creepy Monotone, only shows his cybernetic eye, and utters the famous line "I'm sorry, but I cannot do that".
He also starts filling the tower with a green gas that looks like the neurotoxin from Portal.
When attempting to communicate via pictures Raven draws Darth Vader's helmet to represent "force". For clarification, she was attempting to say "You can't force me to have fun all the time".
One of the ponies Raven plays with has a blue mane and pink fur, like Firefly from generation 1 of My Little Pony. Firefly happens to be the favorite pony of Lauren Faust, who created Friendship is Magic, where Raven's voice actress plays the lead pony.