Nothing earth-shattering here.
You open 2♣, strong, artificial, forcing.
Partner bids 2D, GF and waiting.
You bid 2♥, intending a Kokish start.
Partner bids 2♠, the relay. As an aside, hopefully 2♠ denies something. It would be a shame to just bid 2♠ on any old hand and miss the opposrtunity for any number of other possible calls. But, that's another issue...
You bid 2NT, unlimited big balanced.
Partner bids 3♣, Puppet Stayman.
You bid 3D, showing some four-card major. I wish you were playing Batchelder Puppet, as then the issue I am about to discuss would not come up. But, your partner is lazy and refuses to play a decent version of Puppet Stayman. So, what can YOU do?
Partner bids 4♣, showing both majors.
If your partnership is lazy enough to have this auction so far (the jab is in good fun, of course), then you might not have discussed Opener's options at this point. However, it seems rather simple. Opener has already bid hearts (way back when he bid 2♥), and Responder has already bid spades (at 2♠). In fact, the LOL's you are playing against are giggling right now because you have bid every suit, and notrump, in order, almost twice over (until one of you decided to bid Gerber). So, it seems that there are two schemes:
1. Opener bids game the the major of preference or does something intriguing to invite or place a slam of choice, without any clue why.
2. Opener transfers to the major of choice and passes, answers RKCB for that suit if asked, or uses RKCB to ask in that suit if Responder does not but Opener is interested, or any other interesting and useful call, with the major agreed.
It seems fairly superior to use transfers here.
Note how dumb a 4D call by Responder, instead of 4♣, would be. Micropreemption, again. Even if Responder "ain't got no interest at all," that fact has no bearing on whether Opener might or might not have a 28-count. For that matter, Opener seems more likely to have a 28-count if Responder has garbage. So I suppose 4D should be a possible bid but should show some very specific holding, like one major King and nothing else, or two Queens and nothing else, or whatever specific meaning makes sense to y'all.