Recipients of the Webby Awards, which recognise the best of the Internet, are required to make their speeches short and snappy with just five words or less.
Seinfeld, who won Outstanding Comedic Performance for his web series Comedians in Cars Getting Coffee, quipped, "Why five words? It doesn't..." and Spacey stated, "The Oscars should do this" after picking up a prize for his Netflix series House of Cards.
Canadian singer Grimes, who was named Webby Artist of the Year, darted offstage after going over the limit, telling the crowd, "This is more than five words. Six, thanks!"
Other winners at the 17th annual ceremony, which were previously revealed on 30 April (13), including R&B star Frank Ocean, who was the Webby Person of The Year.