Before we go on, you need to be aware that a Tijuana Bible is an 8 page adult comic. They depict people or comic book characters having sex, so if any of this offends you or makes you uneasy, don't keep reading.
For the rest of us, let's talk about Tijuana Bibles. These books started appearing in America sometime in the 1920's, appear to not have been circulated widely, and the artists and writers remain largely anonymous. The name was likely coined in Southern California in the 1940's, as people believed they were brought over from Tijuana, Mexico. Characters such as Popeye, Betty Boop, and real people such as John Dillinger were depicted in these comics. Archie was even targeted for a few of them as well. I have a couple in my collection, but I couldn't tell you how many there are total. As far as collecting them, it's not an impossible task. They run anywhere from $5-50 bucks depending where you go. They are largely crude and offensive, but also fascinating. These books were the pioneers for the underground comic scene, and the concept has evolved and changed. Parody adult comics still exist today, and in some part it's thanks to Tijuana Bibles.
The few Archie related ones I've seen depict Archie with Betty, Archie with Veronica, one of them has Reggie in it. Currently, a good deal of Archie fans are upset over the relationship between Archie and Ms. Grundy in Riverdale. Some people feel it's only there for shock value. Some people like the twist and feel it adds something. Either way, people are talking about it. Which ties into our topic: There is a Tijuana Bible out there that features Archie and Ms. Grundy getting it on.
There's not much to the comic. Archie has to stay after school for throwing spit balls, but Ms. Grundy has other plans for him. They do indeed get it on, and it's as crude and gross as you can possibly imagine. But none the less, the Archie/Ms. Grundy dynamic was a thing before Riverdale, even though it's far from canon. But none the less, here we are. This is a real comic. Clearly someone 30+ years ago thought this would be a good topic for an adult comic. Maybe the writers of Riverdale saw this and had a light bulb moment. Ok, they probably didn't, and I can't justify why it's a plot point. I'm still a fan of Riverdale regardless.
So there. Archie's been hot for teacher since before I was born, and while it does make my skin crawl, Tijuana Bibles are a small part of pop culture history. A dirty, fascinating part.