okay im directing all possible brainpower towards this it's so important
so it happens during the song of the witches- accidental demon summoning and bam he's in david tennant's body. what ensues actually isn't all that different from the original performance, you just hear "stop it that tickles" occasionally over the headset
crowley would kinda twig that he's somehow in the middle of macbeth (just because he likes the funny ones doesn't mean he hasnt seen macbeth a thousand times... even if only to take the piss out of it each time afterwards to annoy aziraphale), and he kinda like. dips in and out of remembering the lines. the audience doesn't care about (or lbr, notice) his ad-libs bc as far as they're concerned, rsc legend david tennant can do what he fucking likes
sword fight, he makes light saber sound effects to each blow. then eventually we come to the curtain call, and he is actually pretty pleased with himself but mainly because whilst 'dead' he drew a penis on the stage in the fake blood
the pièce de résistance however is that he spots michael sheen in the crowd, and swan dives off the stage to be carried towards him, thinking it's aziraphale. the audience happily passes him over their heads, bc honestly david tennant crowdsurfing his way to michael sheen is probably the least ridiculous thing either of these freaks has done to be in each other's company