Washington (CNN) The impeachment inquiry into President Donald Trump has already seen it all: contentious public hearings, unexpected bombshells, testimony implicating the President and a fair share of conspiracy theories. The drama could escalate even more in the coming weeks as Congress moves to the next phase and preps for Trump's potential trial in the Senate.

House Democrats spent the last two months interviewing witnesses and preparing their case against Trump. The House Intelligence Committee is now writing a report that will detail the allegations that might make their way into formal articles of impeachment. Another committee has scheduled a public hearing for Wednesday to delve into the constitutional issues at play.

"This is a much more dynamic situation" than the impeachment of President Bill Clinton, said CNN legal analyst Elie Honig. House lawmakers are running their own inquiry into Trump, instead of taking up recommendations from an independent counsel like they did in 1998.

It's a safe bet that House Democrats will vote to impeach Trump, which would trigger a public trial next year in the Senate. Witnesses could be called back to testify, and new players might get involved, too. This is a rarely-ventured corner of American democracy, and there will be new twists and turns while senators deliberate whether they should remove Trump from office.

Ahead of these pivotal steps, here's a look at five surprising moments from the House impeachment inquiry that captivated Washington and could shape what comes next.

Pivotal call at a Kiev restaurant

During the first public hearing, US diplomat Bill Taylor made an unexpected announcement : He had recently learned that his aide overheard a phone call where Trump talked about Ukraine possibly announcing investigations into former Vice President Joe Biden. Not only that, but the presidential phone call unfolded in public, at a crowded restaurant in Kiev.

The revelation kicked off a frenzy. Reporters scrambled to figure out the identity of the aide. Democrats hastily scheduled a closed-door deposition. The aide, David Holmes , eventually told his story to the public at an impeachment hearing last week, explaining that he overheard parts of a July call between Trump and US Ambassador to the European Union Gordon Sondland

Under oath, Holmes told lawmakers , "Ambassador Sondland replied, yes, he was in Ukraine and went on to state that (Ukrainian) President Zelensky, quote 'loves your ass.' I then heard President Trump ask, so he's going to do the investigation? Ambassador Sondland replied that he's going to do it, adding that President Zelensky will do anything you ask him to do."

After the call ended, Sondland told Holmes that Trump "did not give a s--t about Ukraine" and only cared about the "big stuff," like the Biden investigation, according to Holmes' account.

The riveting testimony further tied Trump to the effort to squeeze Zelensky and hurt Biden's campaign. It was a startling twist, because few had ever heard of Holmes when the inquiry began. By the end of the public hearings, his face was plastered all over national television.

Real-time witness intimidation?

Trump scored an own-goal during one of the hearings thanks to his own tweeting.

On the witness stand was Marie Yovanovitch, the career diplomat who US ambassador to Ukraine until her ouster earlier this year. Trump recalled her from the post amid a months-long shadow campaign against her, filled with lies, mounted by some of Trump's closest allies.

Yovanovitch was there to tell the story of her ouster, which is an important part of the Ukraine scandal but had always been a secondary plot point to Trump's potentially impeachable dealings with Zelensky. But things went off the rails after Trump got involved with a tweet , attacking Yovanovitch and blaming her for problems in the countries where she served.

"Well, it's very intimidating," Yovanovitch said, during the hearing, about the Trump tweet. "I can't speak to what the President is trying to do, but I think the effect is to be intimidating."

The text of the tweet could hardly justify a criminal charge for witness tampering, but Democrats pounced nonetheless. Some top Democrats suggested they might include Trump's attacks against Yovanovitch in an article of impeachment for obstructing Congressional proceedings.

Trump ally implicated nearly 'everyone'

A lot can change between a closed-door deposition and a nationally televised hearing. That was true for Sondland, the neophyte diplomat who donated $1 million to Trump's inauguration.

Sondland was initially viewed by many as a Trump-friendly witness who might stick to the party line, even though he did defy State Department orders and show up for a deposition.

But things started unraveling pretty quickly, and Sondland was forced to revise his testimony with a sworn statement saying that he told a Ukrainian official they likely wouldn't get the frozen US military assistance until Zelensky announced the "investigations," a reference to the Biden probe.

Then, when it was time to testify in public, Sondland really turned up the heat . He confirmed, in explicit terms, that there indeed was a "quid pro quo" in the works, where a White House invitation was withheld until Zelensky announced the investigations into Trump's political rivals.

"Everyone was in the loop," Sondland said repeatedly, describing how he discussed the scheme with Vice President Mike Pence, Secretary of State Mike Pompeo and acting White House chief of staff Mick Mulvaney. All three top officials have disputed parts of Sondland's sworn testimony.

These top officials all ignored subpoenas, so it's unlikely they'll ever be forced to give these denials under oath. But Sondland's testimony put them in the hot seat more than ever before.

Ukraine knew early about aid freeze

One of the lesser-watched impeachment hearings brought a bombshell of its own.

Senior Pentagon official Laura Cooper was sworn in after Sondland's gripping appearance on Capitol Hill, which dominated the day. But Cooper provided new information that Ukrainian officials asked her staff about the stalled military aid as early as July.

The revelation blew a hole in the GOP defense that Ukraine couldn't have been pressured by Trump because they only learned from news reports in late August about the frozen assistance.

It wasn't entirely clear from Cooper's testimony just how much the Ukrainians knew. But Cooper said her staff got emails from a Ukrainian official on the day of Trump's call with Zelensky, and they wanted to know, "what is going on with Ukrainian security assistance?" she recalled.

The Pentagon has refused to turn over documents to House committees, so impeachment investigators and the public may not see the underlying materials anytime soon.

Budget officials quit amid frustration

The last person to give a private deposition, budget official Mark Sandy, gave lawmakers a bundle of new information . But strangely, he hasn't been called to testify at an open hearing.

Sandy, a senior career official at the Office of Management and Budget, described how one of Trump's political appointees took responsibility for the Ukraine portfolio once he started raising concerns. Until that point, Sandy had signed the paperwork officially imposing the delays.

Not only that, but Sandy also testified that he was part of a group of career officials who sent a memo recommending that the freeze be lifted because it was hurting US national security. This helps Democrats make their case that Trump undermined US interests for personal benefit.

He also testified that two OMB officials quit amid the turmoil over the Ukraine funding, which included unaddressed concerns that the holdup could have been illegal. Sandy couldn't say for sure that the two officials resigned solely because of the Ukraine affair, but he said both officials were frustrated by the situation and that they made their disagreements known before quitting.

The officials were not named in the transcript of Sandy's deposition. A senior Trump administration official disputed his testimony and said nobody quit because of the aid holdup.

This story has been updated with additional developments Friday.