After having been told that they're unreliable, a member of the Sanzenin SP tells Maria "there chances of winning against a butler is as low as a natural trying to beat a coordinator". This is a reference to the genetically enhanced humans known as the coordinators from Mobile Suit Gundam SEED.
The transmitter Maria used to track Nagi's location in Hakuo Academy is labeled "Somy". This is a parody of Sony.
While at her brithday party. Hinagiku is forced to sing the opening theme to Neon Genesis Evangelion.