Metacarcinization
Metacarcinization
[White Hat and Cueball are walking together.  White Hat has his smartphone out in his hand. White Hat: Have you seen this video of a crow sledding on a roof? Cueball: Yeah! It's always cool to see animals using tools. Cueball: Like how sea otters use rocks to open crab shells. Cueball: Hey, did you know the "crab" body plan has evolved multiple times?
[Caption below the panel:] Regardless of the starting topic, any conversation with me eventually converges to carcinization.
The comic strip opens with a conversation between White Hat and Cueball as they are walking together.  White Hat asks Cueball if he has seen a video of a crow sledding on a roof — presumably this one , or one of its later viral reposts. ( Animals sledding seems to be a thing lately). In this case, the crow is a Hooded Crow . Cueball remarks that it's a cool example of tool use by animals , a sign of intelligence (which corvids [Corvidae; the crow family], including crows, ravens, and jackdaws , are famous for).  He then points out that sea otters use tools too, namely using stones to crack open crab shells.
This in turn leads him to bring up the fact that the 'crab' body plan has evolved multiple times, a phenomenon known as carcinization , previously discussed in 2314: Carcinization .  In that strip, Cueball turned into a crab shortly after hearing about carcinization, so perhaps White Hat will likewise be transformed momentarily.
The conversation serves as an example of a wiki walk , where a conversation naturally diverts from the original topic into a seemingly unrelated topic through a series of logical associations. Although a sledding crow has little to do with carcinization in and of itself, the conversation has managed to bridge the two topics through intermediary steps (crow using a sled, animals using tools in general, otters using stones to open crabs, crab evolutionary process).
The title and caption is a joke that, much like natural life-forms have evolved into crab-like forms multiple independent times, so too do all of Cueball's (or Randall's) conversations wiki-walk into a discussion of that evolutionary process.
In the title text, Randall jokes that marine biologists have a similar tendency to bring up whalefall (or "whale fall") ecosystems, which arise whenever a whale's carcass falls onto the deep ocean floor and are thought to provide "stepping stones" for species migration across the generally barren seafloor.  Such occurrences are relatively rare, perhaps occurring once every few miles on whale migration routes, but they happen anyway, much like conversations about them. Another example of scientists tending to bring up facts from their field of study can be found at 1610: Fire Ants , and Randall often brings up the fact that birds evolved from dinosaurs.
[White Hat and Cueball are walking together.  White Hat has his smartphone out in his hand. White Hat: Have you seen this video of a crow sledding on a roof? Cueball: Yeah! It's always cool to see animals using tools. Cueball: Like how sea otters use rocks to open crab shells. Cueball: Hey, did you know the "crab" body plan has evolved multiple times?
[Caption below the panel:] Regardless of the starting topic, any conversation with me eventually converges to carcinization.