Watch 2015 Super Bowl Ads on Tumblr

The Super Bowl's ad games have been underway for weeks now, but there are still some surprises left.

More than 20 ads already have already been posted online by companies hoping to capture social media attention in the days leading up to the big game.

[WATCH 2015 Super Bowl Ads on Tumblr]

But Coca-Cola, Turbo Tax and Weight Watchers are among those waiting to unveil their full ads to the more than 110 million viewers expected to watch the New England Patriots and the Seattle Seahawks.

"If you're waiting to show your commercial this year, you have to be very confident that you're good enough to attract attention just on game day," said Tim Calkins, marketing professor at the Kellogg School of Business at Northwestern University.

Companies will of course also have teams of employees hoping to score with clever, well-timed posts on social media throughout the game. One of the most memorable moments from the 2013 game, for example, was a tweet from Oreo. When a blackout hit the stadium early in the game, the company posted an image of an Oreo cloaked in darkness with the tagline "You can still dunk in the dark."

It got more than 10,000 retweets on Twitter within an hour.

This image provided by Henkel shows a portion of the company's Loctite glue television ad schedu …

Here's an early look at what to expect. Check back throughout the night for updates.

- Associated Press