Super Bowl advertisers had only moments to make their on-air pitch, but several of them, including PepsiCo, H&R Block, Overstock.com and E*Trade Financial, used the microblogging site Twitter to keep the conversation going before, during and after their commercials aired.

E*Trade’s talking baby told viewers to “check out me and my boy Benny” and said he was hosting a post-game “onesie” contest. Pepsi’s SoBe lizard, which starred in a Life-water commercial alongside three dancing football players, “Tweeted” thank-yous to fans of its ad and frowning faces to disparagers.

According to marketing firm New Media Strategies, there were nearly 49,000 posts on Twitter that referenced the Super Bowl ads during the game. Advertisers and users followed each other’s conversations by adding “hashtags,” such as “#superads09” or “#superbowlads,” that make Twitter posts easier to search and categorize. While some advertisers maintain a presence on Twitter all year round, keeping an eye on the site during the Super Bowl – when a huge number of people are talking about the same ads, at the same time – is a chance to get a vast amount of input in minutes.

Online retailer Overstock ran a low-key advertisement starring Utah Jazz basketball player Carlos Boozer that fell flat with some viewers, including Georgy Cohen. Watching the Super Bowl in her Somerville, Mass. home, the 29-year-old Web editor posted “Not so good” in response to an Overstock Tweet requesting feedback. 

When Overstock asked her why, she wrote, “No one cares about Carlos Boozer, and it just wasn’t entertaining.” “To their credit, they followed up and wanted to know what I thought,” Ms. Cohen said. “I felt more positive toward them” than she did to E*Trade and SoBe’s Twitter presences, who weren’t as responsive to her commentary.

Patrick Byrne, Overstock’s chief executive, said the ad did receive some negative comments, generally from people who thought it was too subtle. “But that was OK,” he said. “We think it’s appropriate you can join the social discourse, as long as you’re not trying to shape it or do anything under-handed.”

H&R Block used Twitter to host a speedy contest after its “Murray” ad aired, asking users to guess who the voice of Death was. Vic Vijayakumar won a free copy of the company’s TaxCut program after responding “Abe Vigoda” within minutes of H&R’s question. Mr. Vijayakumar, a 25-year-old software engineer in Raleigh, N.C., was set up the way marketers envision these prospective customers to be: watching the game on his TV, with his laptop at his side and a Twitter application running. He was one of the first people to guess correctly, even though he had to watch the commercial again on YouTube.

H&R added about 60 “followers” on Twitter during the course of the game, said spokeswoman Denise Sposato, and created a new account just for its commercial character Murray. Like Overstock, H&R received critical feedback through Twitter, something that’s par for the course on the site. “We know that no ad is going to appeal to everybody,” Ms. Sposato said. Some even suggested new pitchmen for the tax-preparation company. “Several want-ed [Treasury Secretary Timothy] Geithner,” she said.