"Super-duper ultra mega"

Can I use the adjectives super-duper, ultra, and mega in one adjective? For example,

A super-duper ultra mega huge dome.

Sure you could - but I'd restrict it's usage to informal writing, in cases where you wanted to use hyperbole for some dramatic or humorous effect. For starters, the term super-duper is considered slang, so it generally wouldn't work well in a formal document.

Moreover, you have more three adjectives describing dome, meaning that commas are in order. Plus, ultra- and mega- are prefixes, so I'd punctuate the sentence as follows:

On our way through Texas, we visited a super-duper, ultra-, mega-huge dome!

All in all, though, that sentence has rather juvenile overtones - which could be fine, of course, depending on the context.

Sure, if you want to sound like an excited nine-year-old.