They are Oshiete Galko-chan characters, I believe future versions of Galko, Ojou and Otako (3 yrs later) https://twitter.com/suzuki_kenya/status/1227793156181094400/
Anonymous posts can be deleted within one hour of posting. Members can delete their posts any time.
Tips
if a URL fails to load or returns 403 Forbidden, try entering the link manually into the location bar and hitting enter. since some sites have fairly ridiculous hot-link-protection.
link directly to an image if you can
avoid posting video links, facebooks links, private sites. i don't use Flash, or have a FB account - same probably goes for other people =P
we use a LAME filter on all anon posts. although reasonably restrictive, if it affects you, consider logging in to disable it, or write a less commercial/cheesy/offensive post!