When Starfire misses Robin, she remembers some events from past episodes: The ferris wheel ride from Sisters (2003), the prom dance from Date with Destiny (2004) and the balcony scene from Betrothed (2004).
When Beast Boy dons the Robin costume, he breaks through a paper mache ring held by Starfire. This is an exact recreation of the cover for "Detective Comics" #38 - the First appearance of Robin - declaring him the "Sensational Character Find of 1940." Beast Boy is declared the Sensational Character Find of 1965, which is the year of Beast Boy's first appearance in "Doom Patrol" #99. The inclusion of this cover homage is another subtle hint by the creative team to subtly tell viewers that the Robin on this series is Dick Grayson.
This episode was originally aired out of production order. This is actually the fourth episode in Season 4, but it was the second one aired.