These are pretty common/old:

 

if you were any dumber I would have to water you twice a day

 

You look like survivors or xStarx

 

wow k
pretty uglai tho.
so

 

Yos~

 

Eww what is that smell? Oh it's you.

 

what is that in the distance O.O it looks like garbage, oh wait its just you

 

You look like BOTBaccalord but he's cooler than you, way cooler.

 

I might think of more I'm just keeping it at a couple for now.

 

You look tired

 

hits me deep

 

I'd insult you, but nature did a better job of it than I ever could.

 

You are so ugly that when hello kitty saw you she said Goodbye