Destructoid's Chris Carter praised how Return of the Mammalians interacted with the game's multiplayer modes, by both teaching the player important mechanics and rewarding them with useful items.
Martin Robinson of Eurogamer criticized the lack of significant new content, saying that even the largest new additions are not something "that can be applauded too enthusiastically".
Brian Shea of Game Informer praised the larger amount of content available at launch compared to previous entries in the series, as well as how the game blended new and returning content.
Kotaku's Patricia Hernandez lamented the amount of disconnections while playing online, saying that it is "inexcusable".
Wired's Reid McCarter praised the game's original, cartoony characters, as opposed to brand crossovers and realistic graphics.