Mr Castor began his remarks on Tuesday by praising US senators for their opening arguments, while admitting it forced him to quickly change his.
"I'll be quite frank with you, we changed what we were going to do on account that we thought the House manager's presentation was well done," Mr Castor said at the beginning of his meandering statement.
The lead counsel went on to only mention Mr Trump five times during his bizarre speech, which covered other topics such as ancient Senates in Greece and Rome and founding fathers James Madison, Alexander Hamilton, and Benjamin Franklin.
Mr Castor also caught the attention of viewers during his 50-minute speech, with comments such as “Nebraska, you’re going to hear, is quite a judicial thinking place,” and: “This trial is not about trading liberty for security. It’s about suggesting that it is a good idea that we give up those liberties that we have so long fought for.”
Social media users quickly reacted to Mr Castor’s bizarre remarks on Tuesday, by creating memes mocking the incoherent speech.
George Conway, the husband of Mr Trump’s former senior adviser Kellyanne Conway, responded to Mr Castor’s remarks by tweeting: “WE WANT RUDY,” in reference to the former president’s gaffe-prone personal attorney, Rudy Giuliani.
The attorney led the Trump campaign’s attempts to overturn 3 November’s election results, and was mocked after being involved in several bizarre moments in court and in press conferences, including having his hair dye stream down his face.
Mr Giuliani was referenced by other social media users, with @Acyn writing: “If this was Baseball, Rudy would be warming up in the bullpen.”
Other Twitter users were just confused by Mr Castor’s remarks, with @IlvesToomas writing: “To quote President George W Bush on Donald Trump's inaugural speech, verbatim, ‘Well that was some weird s***.’”
While CNN’s Chris Cillizza posted a gif of The Weeknd looking lost during his Super Bowl halftime performance, captioning it: “Me, trying to understand what Bruce Castor is talking about.”
Journalist Andrew Feinberg referenced a mishap that took place earlier on Tuesday, when a lawyer was unable to change his Zoom filter from a cat, frantically telling the judge: "I'm not a cat."
Mr Feinberg posted a picture of the zoom meeting and captioned it: "Now joining the Trump legal team…", while filmmaker James Gunn replied: "That’s a pretty big upgrade."
Some people wished Mr Trump had not been banned from Twitter, so that he could have live-tweeted Mr Castor's speech.
Quoting Mr Castor, musician and author Tim Burgess wrote: “The American People are ‘smart enough to pick a new administration if they don’t like the old one....and they just did’.”
He added: “Trump’s lawyer seems to be trolling him in real life, now he’s not on Twitter”.
BBC journalist Paul Danahar wrote: “I so wish President Trump had had access to his Twitter account as he watched his defence lawyer ramble his way through that performance at this Impeachment trial.”
While Washington Post journalist Karen Attiah tweeted: “I would personally like to ask Bruce Castor for a refund,” to which fellow Post columnist Karen Tumulty replied: “He works for Trump. He wasn't getting paid anyway.”
Mr Castor ended his speech on Tuesday by contradicting Mr Trump’s long-standing false claims that November’s presidential election was stolen.
Although Mr Trump still falsely claims that Democrats stole the election, his lawyers are arguing that he cannot be impeached because he is no longer a sitting president.
“The American people just spoke and they just changed administrations,” Mr Castor said on Tuesday, while awkwardly making the argument. “They’re smart enough to pick a new administration if they don’t like the old one and they just did,” he added.
Mr Trump’s trial will continue throughout the week, but Mr Castor’s colleague, David Schoen confirmed that the widely mocked attorney will not be speaking on Wednesday.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies