The various bat tfees reacting to the news they're pregnant with their respective first children. Given the time period (Victorian England), most of them didn't have a good sex ed.

-Cards had basically no sex ed, so finding out that it was going to have a pup was a very big (positive) surprise. Since one of its colleagues had a child a few years earlier, Cards had been pining for a baby of its own. Its first pup was conceived pretty much right upon all of its batty plumbing being up and running.

-Doc thought she was too old to conceive, and only went to the doctor because her bat tf symptoms were starting to show. She's very pleased to have a child she always wanted (she couldn't find a "man worth her time"), but she's a bit nervous to tell the sire of the pup since the encounter was a one-night stand.

-Honey is happy to be having a pup, but it's a bittersweet moment. It is bickering with its original mate at this time, and its child was fathered by someone else. The sire initially impregnated Honey under the terms that Honey would raise the pup on its own, but after having daydreams about raising a strong pup, the sire ends up being involved.

-Ash has been planning this pregnancy for years with its mate, and it is very happy, if nervous about its life changing so much. It agreed that once it was pregnant, it'd settle down from life as a locomotive's doctor and live with its mate.