Notes:

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My reasons that might work this crossover:
1.-Both aired in CN (well, space dandy in toonami but is the same, i guess)
2.- Space and psichodelic theme chapters with a ton of heartwarming and tear-jerker moments
3.- Protagonized with an adorable dork with him unique “Dandy way” to live
4.- cool and smooth soundtrack
5.- maybe include hot aliens but depends of the fetish of each one