I guess i'll take a stab at this big one though I might find it hard to describe. Note that I might be HD but I require a few planets to be aligned first. I haven't cataloged it but I think there are quite a few varieties of erection.
1. The Lovie - While kissing my W, feelings of desire sweep over me and the tingle goes down between the legs and up pops mr. happy and it is looking for nice warm place.
2. The Sleepy - Sometimes when you lie down, your whole body relaxes and it sends an overwhelming feeling of comfort through you that culminates between your legs. I'm embarrassed to admit this but I've had this start to uncontrollably happen in very "wrong" situations and it had absolutely nothing to do with where my brain or my desires were. It doesn't happen to me much anymore but I would sometimes have this happen in high school in the early morning. Similar to a morning wood. This can sometimes be converted into a Lovie but I've also had it go the other way when using the sleepy to ML. (maybe I'm not so HD after all).
3. The Morning Woodie - This is just the natural result of your body doing periodic system-checks throughout the night to make sure everything is functioning. Like the sleepy it may or may not be able to be turned into a lovie if the owner's head isn't into it.
4. The Defendor - This is a stiffy that happens when pressure is applied on top of your midsection. Embarrassingly, I've had this happen from putting a heavy bag on my lap...maybe I'm just a closet American Tourister.
5. The Yankie - This is one that comes from MB. It requires a combination of good thoughts and very specific physical maneuvers that only the owner knows. Converting this to a Lovie is very difficult because you are not really in the emotional mood. You are just trying to get off and are using every trick to get the end result. I've tried to convert it to a lovie when I wasn't in the mood and it didn't last (man, once again I'm showing signs that I might be LD).
6. The Monster - This is when a combination of things culminate at once. It's like the Lovie gets a shot of adrenaline because the erotic envirnment is waaay high. Remember my recount of "f*cking the bajeezus out of my W a while back" (to newcomers, that is a clinical expression in PM)? That was the monster. It can only last for about 10-15 minutes. It's owner is usually in the "energizer bunny" position.
Hope that helps. It sounds like you converted a sleepy-defender into a lovie.
Anywhere is walking distance if you have the time
-Steven Wright