Big sun

I am researching English expressions and their usage in American sitcoms, and would like to know if it is possible to say that someone is "a big sun" to indicate that they are excited ("You're a big sun")? I just want to verify in case I got the expression wrong from the program I was watching.

Any help will be appreciated!

"Sun" and "son" sound alike. I'm not familiar with either word used that way. ~rb, U.S.

Could it have been "You're a biggun" (a big one)?