Continuing this thread about how crossovers and references in games could be handled differently, I love the idea of a one-on-one crossover instead of a multi-IP megacrossover - I remember when the SpongeBob Cosmic Shake teaser image was posted I thought it was teasing a crossover with Invader Zim. There's this blob thing that, in the final image, is revealed to be a portal with a big zipper but without full context looks like a piece of Irken archetecture.
It would make sense IMO - if you narrow down Nick's biggest IPs next to SpongeBob, Zim would likely be the best choice for a one-to-one crossover. Loud House, Garfield, and Rugrats don't have worlds that lend themselves well to games; Ren & Stimpy doesn't really have a world at all, just two characters who do anything and go anywhere as long as it's funny; Avatar and to a lesser extent Turtles would be too serious and make SpongeBob feel out of place less in a "fish out of water" sense and more "fish in a chip shop" sense; FOP and Jimmy Neutron have worlds that are to an extent too similar to SpongeBob's and therefore wouldn't have a good juxtaposition factor; and then Zim is an IP that could play off SpongeBob in a comical way, being dark and bruding to juxtapose happy go lucky SpongeBob against, but also a series with loud and silly humour that SpongeBob would fit well into, as well as a unique world both on Irk and Earth to explore in a collectathon setting.