I can somehow imagine DIO finally learning a head reattachment spell but ends up accidentally putting the heads on the wrong bodies the first time
Dio: Good news, everyone! I've perfected the head reattachment spell.
The heads: *chattering and rejoicing amongst themselves*
Dio: Yes yes, now line up
Alessi: Hey, wait a second, boss man. Our heads are all the way in Hawaii!
Steely Dan: I thought they were in Canada
Alessi: No, I got a snap from my stand saying they were in Hawaii right now... BUT THAT'S NOT THE POINT
Dio: Yes yes yes, whatever. Now. Let me do my work *reciting the spell*
Jonathan: oh this is so exciting!!
Erina: I can't wait to embrace-
Steely Dan: Hello?! What about our bodies?!
Speedwagon: DIO IS HAVING TROUBLE WITH RECITING THE REATTACHMENT SPELL AND IS GETTING DISTRACTED
*everything flashes white*
Dio: *is blown back across the room against the wall* unnnghh... *Rubs his head... Sees through the clouds of magic smoke that there are bodies on the ground* Well... I suppose everything worked out in the end.
Erina: Hmm? *Looking at her hands* I'm a bit taller than usual... And this outfit?... Wait. (Jonathan's body)
Speedwagon: Uh, this doesn't seem right *twirling his dress around* (Erina's body)
Jonathan: I lost a lot of muscle... Ow, my liver!! (Zeppeli's body)
Zeppeli: I feel so young and spry! (Caesar's body)
Caeser: Uh... What's going on with those guys? (Speedwagon's body)
*a mysterious figure approaches*
???: DIO!!! WHAT THE HELL DID YOU DO?! I'm fused together with.... WITH.... AAAAAAHH!!! I'm not Alessi, I'm not Steely Dan. I'm Steelessi. Yeeeaarrgh!! You better fix this soon!!
Dio: *wide eyes, rubs his eyes* ..... *Flips through the spell book...* You. Idiots... I told you all to keep quiet. Now you've gone and switched bodies!