Vice President Biden generated the most boisterous responses on Twitter during the vice presidential debate Thursday night.

The audience in the Centre College auditorium — where Thursday night's vice presidential debate between Biden and Rep. Paul RyanPaul Davis RyanWhy the rush to condemn a carbon tax? House votes to go to conference on farm bill House backs resolution expressing support for ICE MORE (R-Wis.) was held — was asked not to tweet for the duration, but that didn't stop the tweets from flying elsewhere. 

Still, the debate generated far fewer tweets overall than the first debate between President Obama and Mitt Romney last week. Twitter's politics team counted just over four million tweets sent related to Thursday's debate, compared to the record-setting 10 million tweets sent for last week's debate.

Biden led Ryan in number of mentions on Twitter during the debate, according to multiple counts, in part due to the online response to his facial expressions and use of "malarkey."

Biden joked "malarkey" was an old Irish term, using it twice within the first 20 minutes of the debate and quickly prompting a nationally trending hashtag: #malarkey. The hashtag was helped along by members of President Obama's campaign staff, including Campaign Manager Jim Messina and Deputy Campaign Manager Stephanie Cutter. 

It was also one of the top four Google search terms associated with Biden during the debate.

Team Obama quickly began promoting a tweet from Biden to show up at the top of tweets using the hashtag #malarkey, as well, a smart move to keep Biden at the center of the conversation.

But it was Biden's persistent laughing and smiling while Ryan spoke that prompted multiple parody Twitter accounts.

MSNBC compared the laughing to the sighing of Al GoreAlbert (Al) Arnold GoreAl Gore warns of 'ominous' record-breaking heat Colbert to Kennedy on retirement: Don't tell me your mind's going because 'you never had one!' Budowsky: Obama remains AWOL for Dems MORE during a debate in 2000, when Gore's reactions seemed to overshadow the content of the debate in later coverage. CNN's Piers Morgan seemed distracted by the smile, but later seemed to come around, saying Biden's expressions were infectious. ABC's Amy Walter didn't think the "laughing/smirking" worked at all, another sign that the laughter will come up in post-debate conversation.

Expect the Romney campaign to say Biden's laughter was a sign of desperation, while the Obama campaign will say Biden was reacting naturally to his opponent's policy claims. Shortly after the debate, the Republican National Committee was already pushing the hashtag #BidenUnhinged, and Chairman Reince Priebus tweeted, "The smirk didn't work."

Updated at 11:42 p.m.