[X] My Assistant

little hippo
How on earth can it be solved?

Oh it's actually easy if you just learn their unique appearance. For example, Twilight Sparkle always has some hearts floating around her. (bottom left of the pic)
Fluttershy will always raise her left hand and smile, as you can see in the upper left of the pic.
Look at the hippo chart linked at the riddle to see all hippos.

...oh, it's just a dumb HV thing. For a moment I thought this was EH's own captcha.

Well, I prefer the cute hippos to the boring Google captchas where you have to solve dozens puzzles with stairs, vehicles and bridges. (IMG:[invalid] style_emoticons/default/wub.gif)

Look more closely, there are tiny cute hippos hiding under the stairs, driving the vehicles and crashing into the bridges!
(IMG:[invalid] style_emoticons/default/ph34r.gif)

(IMG:[files.catbox.moe] https://files.catbox.moe/za7z4r.gif)

...oh, it's just a dumb HV thing. For a moment I thought this was EH's own captcha.

Nah, OP seemed to be talking about bug of 3-rd party client.

[github.com] https://github.com/xiaojieonly/Ehviewer_CN_...strings.xml#L97

Little Hippo is the default username shown.

(IMG:[24.media.tumblr.com] https://24.media.tumblr.com/eb20dbc0a20600ca5444ef72f903f228/tumblr_n1kk604s9B1t4o62mo1_400.gif)