Slang expression translated into Spanish

In today’s “Baldo” comic strip, Baldo fancies himself a king or a sage. When I saw that I thought “You wish!” Is there an equivalent expression for this in Spanish?

I’ve heard ni en sueños, meaning “[not even] in (your) dreams,” which might work okay.

JKellymap suggestion works, just “!Iluso!” (deluded/delusional) would also do, IMO.

Gracias a ambos.

De nada…

I just thought that “¡Ya desearias!” (you would wish) would be a more similar expression.

When I start having delusions of grandeur, my wife will say “bah, estas loco”.
Or she’ll say “en tus suenos”