First of all, I'd like to thank the people who have Musicblock SB-1 for going around and playing them to crabs because without them doing that, making the crab happy was nearly impossible for everyone else prior to that block being played.
So, thanks to the holders of SB-1, I've been able to make all six crabs happy in less than two (real time) weeks without using SB-1 or GNG! Although I do have GNG, it's usually not the best block to play for the crab, so I only play whatever normal blocks, that anyone can get, that I have on me. I've had a total of 21 happy crabs so far and made the final crab (meaning all six of them) happy on the 24th of December.
I didn't crop the screenshots so you could see my username and the different Glitch dates at the top.
December 12: Hechey Track with BB-2; this got me the "Make a Crab Happy" badge - I was so excited to finally get this! :D:D imgur.com/m9dGp
December 13: Hechey Track with DG-4; no screenshot because I wasn't expecting to make it happy so soon after getting the badge
December 13: Karpal Tunnel with DB-1 imgur.com/Tuf13
December 14: Karpal Tunnel with DB-4 imgur.com/5n6Io
December 15: Hechey Track with DB-1 imgur.com/X1yEJ
December 18: Oktyabrya with DR-1 imgur.com/HXaQ4 - after this one, I made it sort of a goal to make the last three happy, but I still play blocks for all of them for the currants and xp
December 19: Uplands Verge with DR-3 imgur.com/uXl2P
December 20: Baby Steppes with DR-4 imgur.com/lhbvT
December 24: Scribe's Weald with DG-3 imgur.com/27Doy
December 29: Hechey Track with XS-4 imgur.com/Neo2L
January 2: Scribe's Weald with DR-1 and Crabato Juice bonus imgur.com/goIz1
January 2: Karpal Tunnel with DR-1 and Crabato Juice bonus imgur.com/ZAEOp (same game day as above)
January 4: Uplands Verge with DG-2
+ 8 more crabs not listed here with the last crab being made happy on February 7th
I'll probably continue to play blocks for the crab because I like the possibility of a full energy and mood refill for making it happy, but it's still also nice to get currants and xp. :)
Thanks to Codex for the tip about crabato juice. Apparently, drinking some and having the "Crab State of Mind" buff while playing a block to the crab gives you double the amount of currants and xp than usual. Making the crab mad (playing a musicblock it just heard) while the buff is active will result in a loss of 20 mood. If you don't have any juice to drink, you can get it from the crab before playing a musicblock by flattering it then hugging it.