Spoilers for Nightwing #89 by DC Comics below
In the latest issue of Nightwing, Teen Titans Go! was just confirmed as being canon in the main Prime Earth DC Universe. In the comic, Dick Grayson and Barbara Gordon are seen wearing their pajamas in bed, with the heroine sporting a Teen Titans Go! T-shirt, while the former Robin wears Batman PJ pants. It's an amazing reference the popular animated series.
Teen Titans Go! is a spinoff of the original Teen Titans animated series, with all of the main voice actors reprising their roles for the zany children's show. Teen Titans Go! is a comedy-based, irreverent version of the Teen Titans with a younger audience in mind. Robin (Scott Menville), Starfire (Hynden Watch), Cyborg (Khary Payton), Raven (Tara Strong), and Greg Cipes (Beast Boy) make up the cast of characters, as the series focuses on their adventures inside and outside Titans Towers. In addition, the series was turned into a full-length musical comedy in Teen Titans Go! To The Movies, which was a critical and box office success.
In Nightwing #89 by Tom Taylor, Bruno Redondo, Adriano Lucas, and Wes Abbott, Dick Grayson is awoken in his Bludhaven apartment by his girlfriend Barbara Gordon. She informs the sleepy hero a robot is petting their dog. Nightwing takes one glance at Haley and sees a robotic hand, leading him to throw one of his Escrima Sticks at the mysterious foe. It turns out to be Superman's robot Kelex, who informs Nightwing that Superman has asked him to seek out Jon, who needs his guidance. As Nightwing stands up and reveals his Batman pajama pants, Gordon is seen wearing a Teen Titans Go! T-shirt.
It begs the question, does the Teen Titans Go! animated series exist as a show within the DC Universe? It would make sense that there would be cartoons based on real-life heroes, but there's no definitive answer. However, the fact Barbara Gordon wears a Teen Titans Go! T-shirt at least confirms the team exists in some form in canon in the DC Universe.
Tom Taylor, Bruno Redondo, and the entire creative team for Nightwing have done an excellent job injecting personality in life into Dick Grayson's ongoing series, so to see him wearing Batman pajamas and Barbara Gordon wearing a Teen Titans Go! T-shirt helps humanize the characters in a fun way. Readers can see Barbara Gordon's Teen Titans Go! shirt in Nightwing #89, now in comic book stores.