Sonic World Adventure Rush has numerous shout outs to various corners of the Sonic universe. Here is a concise list with cross references where need be.
Main List of Shout Outs:
Captain Westwood, in the comics he was taken from, was heavily modeled after Albert Wesker of Resident Evil fame, so much so, he became a traitor to all parties involved at some point. These traits carry over into the story.
Most of their junk food derived from the characters Improbable Food Budget has humorous names that reference the far corners of the Sonic universe. Products include:
While writing Ashura's dialogue, the author realized he was subconsciously writing him as the Tenth Doctor, despite not watching much of the show at all. In a case of self Ascended Meme, it stuck and wound up handing out Lampshades to everyone.
Which resulted in Mephiles being written with a dash of The Doctor's nemesis The Master, but owing a lot more to Count Iblis of Battlestar Galactica with his air of ambiguity. He also owes alot to Legion.
Morgan laFey (portrayed by Shade the Echidna), raises the remains of the true King Arthur (Sonic). The whole thing, down to the line "Rise from your gave" is a big shout out to the Genesis classic Altered Beast.
Nack the Weasel is known by his Japanese name Fang, and acts as a thief/rouge type. His competition in claiming the reward on slaying the Ilwolf? Ever play Popful Mail?
In Nack The Weasel's Story:
Nack remarks that he wasn't going to kill Bean's brothers Bin and Pin. Those two originated in Dynamite Dux. Bean was designed for Sonic the Fighters explicitly as a reference to this game, as they were both made by Sega's AM 2 arcade division. Bean's alternate costume is Bin!
Nack and Bark are disturbed by Bean's love of KFC. Considering they were a blatant Product Placement in Dynamite Dux in the arcade, perhaps the craving runs in the family?