The most fascinating aspect is that the old members do play along and appear as if they don't know what's going on, as we have today, many threads have been opened for questions, and some other members who offer signature service management have made jaw tantalizing rates threads to fool participants.
Theymos always appear serious about it with the support of some extremely reputable forum members, which makes the joke interesting. Most of the time, the jokes are always about something very difficult and the majority of forum users will not be happy if it is implemented.
Kudos to OP for taking the time to compile all of these Theymos April Fool's Day events from 2015. However, this Captcha is challenging because the more difficult the next one is to solve, the easier the first one was.
To be honest at first it really surprised me about the part that say users that failed the recaptcha will be banned from next week because I did actually play and try to solve the recaptcha but menhh the more I try the harder it felt and like you said power glove and some other users like Fillipone took it very serious and I won't lie I really had a bit of a scare hearing about banning of account because the game felt impossible on mobile but it was just an April fools day trick. Nice one though and I never knew the tradition has been on for this long @2015 till date.