This is a topic that has been egging me for ages. I even "asked" Jeff Parker about it via a blog comment once.
All Rulk readers know of this. Back a while, Red and Thundra made a deal to help get her back to the future to conceive Lyra. She then smooches him, seeming as a way of thanking him.
Excuse me, isn't Thundra the one who steals male DNA from kissing them? For all we know she genetically engineered another baby from stolen Rulk DNA!