You know when you're stuck on something because it's so inconsequential it doesn't matter? I've spent the last half hour trying to think of authentic sounding magic words that a cheesy nightclub magician might say. Abracadabra, Piff, Paff, Pouf, Izzy Wizzy Let's Get Busy kind of thing.
It doesn't have to be funny, in fact it would detract from the joke if it was too funny or unusual. It just has to sound vaguely believable. Any suggestions?
Zim-zala-bim
Plugh!
open sesame
When shall we three meet again
in thunder lightning or in rain?
Mahatta-sark-al-adna
Allah kazam 
Shizam
Piff paff poof is my favourite!
Widdlypingpongsheeeewham.
I vote Alakazam.
veneficus vox
kjs
Gazumber.
And now. Right before your very eyes, ...
Woopah!
as a cheesy nightclub magician, he might say..
Oh shi... that's not meant to happen!
When I used to do a bit of stand up magic I used the expression 'Kylie Minogue', as the magic words, don't know why but people always laughed. Maybe it's the internal rhythms of it juxtaposed with it's inappropriateness.
SHAZAM!!!!
Om nam shibam.
Or: "I shall now say the magic words: "f**king sorted" and look, the rabbit is on fire.
Google is always great for when you're stuck like that.
.... abracadabra, alakazam, hocus pocus, presto-chango, shazam, and sim sala bim, to lesser known gems like the tongue-twisting tirratarratorratarratirratarratum, to whimsical modern inventions like izzy wizzy let's get busy,
I remember as a kid, my mum would have said to me, 'What's the magic word?' Of course, 'what' wasn't the magic word as the correct answer was 'please'. On reflection, I should have said 'Abracadabra' but I got enough hidings.