In our campaign, the party is preparing for the inevitable epic battle with a super strong BBEG in a couple of sessions.
They were inspired by an awesome scene from the Vox Machina animated series where the bard somehow casts an illusion of the whole party mocking the dragon, while the "real" party is hiding in the opposite corner of the dragon's cave and preparing their combo to finish the distracted dragon.
The party wanted to do something similar to the BBEG, so they've shown me the most viewed and the most liked "Vox Machina spell breakdown video" which states that this illusion trick is simply the "level 3 Major Image spell".
But when I read the description of the Major Image spell, it seems that it's not possible to create 6 "alive" party members at once with this spell (especially so that the fake party members will speak and overall will look natural even to the smart Dragon). Or maybe the whole party is simply treated here as a single object? Like, "image of a party mocking the dragon"?
If Major Image is not an option here, then what possibly could be done to actually replicate such a cool trick in our D&D game? Some other spell? Or it's basically impossible and this scene in the series is just an "artistic liberty" or "rule of cool"? Based on your DM-ing experience, should I just come up with a house rule and say to the party "I'll allow such a trick, but you'd have to upcast the Major Image spell using a much higher level slot and the bard will have to succeed a DC20 performance check" or something like that?