Fullkrug netted the only goal of last week's first leg, giving Dortmund hope of a first final in the competition since losing to rivals Bayern Munich in 2013, also at Wembley.
Contrasted with the glamour of PSG and their hometown superstar Kylian Mbappe, the workmanlike Fullkrug is cast in the image, not only of the current iteration of the team under Dortmund-born coach Edin Terzic but the club's broader identity itself.
While Dortmund remain underdogs against cash-rich PSG despite their slender advantage, Fullkrug has experience in overcoming the odds.
A late bloomer who did not play Champions League football until this season, Fullkrug's hopes of reaching his full potential were undermined by a string of serious injuries.
Four times in his career he has missed more than half a season's worth of games, most notably from 2019 to 2020 when he tore an anterior cruciate ligament.
Fullkrug represented Germany consistently at youth level but did not make his senior national team debut until 2022 when he was just three months shy of 30.
He has 11 goals in 15 games - a testament to his quality in a German side which has regularly failed to impress recently.
Fullkrug joined Dortmund last August from Werder Bremen, where he had won the previous season's Bundesliga top scorer trophy.
A Bremen academy product, Fullkrug - nicknamed 'Luecke' ('Gap') for his missing front tooth - bounced around several clubs before returning in 2019. He played a key role in Bremen's promotion back to the top flight in 2021-22.
With Euro 2024 on the horizon, Fullkrug is Germany's first-choice striker. He was the only member of Dortmund's squad to get called up for the recent Germany friendlies by coach Julian Nagelsmann.
Former Juventus and Italy striker Alessandro Del Piero lavished praise on Fullkrug after the PSG first leg, saying he was "on another level."
"He's not that fast, not that strong, but he's so effective. He's underestimated," Del Piero, now a TV pundit, told CBS.
"He's a real threat in the penalty area. He's a real striker.
"We saw his goal, but in the first half he has an opportunity to shoot, but he calmly gives the ball to Marcel Sabitzer. A wonderful pass."
'It means nothing yet'
While not many people expected either Dortmund or Fullkrug to be in the Champions League semi-finals even a few months ago, the striker said he always believed in himself and the team.
"If I couldn't imagine it, I don't think I'd be here playing Champions League and playing for the national team," he said.
"But I'm very happy to be here because we as a team deserve to be in the semi-finals.
"It's good to be 1-0 up but it means nothing yet. We need to work well this week to be prepared for the second leg."
Champions League winners Dortmund do have some experience of going deep in the competition.
Both Mats Hummels and Marco Reus, who announced on Friday he would leave the club at the end of the season, played for Dortmund in the 2013 final.
Niklas Sule was on the victorious Bayern Munich side which beat PSG in the 2020 showpiece.
The pressure will be on Paris on Tuesday.
The freshly crowned Ligue 1 champions' main goal under their Qatari owners has been to lift the Champions League, while Mbappe's expected exit has raised the stakes.
A win or a draw in Paris will take Dortmund, who are fifth in the Bundesliga, through to the final, the next stop in an unlikely journey for both the club and their gap-toothed striker.
