should be pop up vs should pop up

Some examples from the web:

• You should be seeing the Trojan pop-up... now.
• Pop one Trinny, two more pop up.
• The pop-up club had popped up at the perfect time.
• Opened her electronic belly up like a pop-up book.
• There's a chance some personal photographs might pop up.
• When that nativity display pops up at the top of the high street.
• I can't bother you two with every little thing that pops up.
• Your faculty permission has arrived for your pop-up.
• They'll pop up sooner or later.
• They just pop up. Zap! Faces like this one.
• We've got people every place he might pop up.
• It's like air under the linoleum - it pops up somewhere else.
• No matter what pops up or breaks out.
• We tend to pop up where you least expect us.
• So I've invented a new kind of pop-up ad.
• See if her photo pops up anywhere else.
• I might pop up to the city.
• It was a Gallagher pop-up party.
• I met her in a pop-up window on the Internet.
• Whatever pops up on his phone will appear on this.

Some examples from the web:

• An encrypted code should pop up if you enter the wrong password.
• Save your work, select FiltersScript-FuRefresh Scripts, run the script and a new image should pop up. It will probably contain garbage (random colors), because we haven't erased it. We'll get to that in a second.
• We should have a sign pop up...
• All right, the pop-up should be one single, fluid motion.
• Nurse... you have my mobile, should anything... pop up.
• Pop one Trinny, two more pop up.
• The pop-up club had popped up at the perfect time.
• Opened her electronic belly up like a pop-up book.
• There's a chance some personal photographs might pop up.
• When that nativity display pops up at the top of the high street.
• I can't bother you two with every little thing that pops up.
• Your faculty permission has arrived for your pop-up.
• They'll pop up sooner or later.
• They just pop up. Zap! Faces like this one.
• We've got people every place he might pop up.
• It's like air under the linoleum - it pops up somewhere else.
• No matter what pops up or breaks out.
• We tend to pop up where you least expect us.
• So I've invented a new kind of pop-up ad.
• See if her photo pops up anywhere else.