OK i saw the whole series a while back and this is exaclty what happened... ill use spoiler tags:
[spoiler]First kibito-shin transpoted goku and this two guys i forgot the names from the oca dimention, then old kai shows him whats happenning with bebi. goku wants to go of course, but kai tells jim he suld undergo a special training before he goes, and this training was nothing but to turn this wheel to crush cofee beans, Goku butt begins to itch and i found it very funny.
After a while thesituation with bebi was very bad, so goku gets desperate and old shin says him to show him his butt O_O lmao, so then he said he would try to take out teh tail by force (the special training was to get the tail out) so one of the dudes kibito-shin transported turned into a giant twizers and they all began to try to pull out his tail, this of course was very painfull and after a while they decide to tie up goku in a rock, this didnt didnt work so goku tehn sugest to tied up old kai to the rock with the twizers, then goku tries to fly away, while flying away he turns into ssj (dont remeber the level) and the tail was out for good. [/spoiler]
Now old kai didnt want to do this from the bigining becouse goku woulld lose his mind if he went onzaru, so teh special training was to bring the tail out and for him to control his power.