I used to participate in a chat room that allowed a limited subset of HTML, and one of the tags was <marquee>. I played around with this a lot and discovered that you could nest marquees and make (very) limited ASCIImations. This culminated in someone making a ASCIImation parody of Finding Nemo. Good times.
I didn't know what that did so I googled "marquee html", they have a nice little easter egg for it. It's been a while since I've seen anything like that from google