A brief lesson on the origin of mitochondria and symbiosis.

Hank introduces meiosis, a special type of cell division that is necessary for sexual reproduction. He compares and contrasts it with mitosis, as the processes are similar.

A new ice cream shop opens up in town, and Brain does not trust their whimsically-named flavors. When he suspects that their flavors are using fancy names to obscure the classic flavors, he takes matters into his own hands with an investigation.

Beakman explains what allergies and allergens are. He talks about how the immune system causes the allergic reactions through the production of histamines. He uses a clip to show how a sneeze happens physiologically.

Panda and Clifford are having a fun time together when Clifford realizes Panda is using him to get close to his sister, Lucy. While running away from Panda, Clifford accidentally gets peanut butter all over himself, and he experiences a severe allergic reaction, causing his face to swell and his breathing to slow. Panda looks for the allergy pen to save Clifford and experiences a similar allergic reaction. Despite his condition, he manages to save Clifford, who in turn saves him with another allergy pen.