Teenage Borussia Moenchengladbach midfielder Wael Mohya received a surprise call-up, with Germany playing away against Serbia and at home versus the Netherlands in Berlin.
Having named 44 players in his first Germany squad as he hoped to get a better idea of the talent at his disposal, Klopp was forced to cut a number of established internationals and younger talents.
Nick Woltemade, Karim Adeyemi, Nadiem Amiri and David Raum were among those left out of the squad, while Jamal Musiala and Serge Gnabry are still out with long-term injuries.
"After having a 44-man roster in September, it was difficult to make these choices - though, in a positive sense, that's actually good news, as more players deserved to be included," Klopp said.
"The more quality you have at your disposal, the more challenging - in a good way - it is to make the decisions you have to make."
Former Liverpool and Borussia Dortmund manager Klopp was named Germany coach in the summer after the four-time world champion's third successive early World Cup exit.
Germany were eliminated at the last-32 stage by Paraguay in the 2026 World Cup, having been eliminated in the group phase of the 2018 and 2022 editions.
Appointed until after the 2030 World Cup, Klopp spoke of a need to select a younger side with a focus on long-term development, but was unable to ignore 33-year-old Fuellkrug's red-hot form.
Since returning to Werder Bremen in the summer on a season-long loan from West Ham, Fuellkrug has 12 goals in 10 appearances in all competitions, having scored in all but one of his matches.
Mohya, 17, was not named in Klopp's previous squad but the attack-minded midfielder has had a strong start to the season with Gladbach. RB Leipzig's Brajan Gruda, on loan from Brighton, was also called up alongside Stuttgart defender Finn Jeltsch.
Germany face Serbia in Belgrade on November 13 and host rivals the Netherlands in Berlin three days later.
Germany squad
Goalkeepers: Alexander Nuebel (Besiktas), Marc-Andre ter Stegen (Ajax), Jonas Urbig (Bayern Munich)
Defenders: Waldemar Anton (Borussia Dortmund), Nathaniel Brown (Bayern Munich), Finn Jeltsch (Stuttgart), Maximilian Mittelstaedt (Stuttgart), Nico Schlotterbeck (Borussia Dortmund), Jonathan Tah (Bayern Munich), Malick Thiaw (Newcastle United), Philipp Treu (Freiburg)
Midfielders: Tom Bischof (Bayern Munich), Said El Mala (Cologne), Brajan Gruda (RB Leipzig), Lennart Karl (Bayern Munich), Joshua Kimmich (Bayern Munich), Wael Mohya (Borussia Moenchengladbach), Felix Nmecha (Borussia Dortmund), Aleksandar Pavlovic (Bayern Munich), Derry Scherhant (Freiburg), Florian Wirtz (Liverpool)
Forwards: Younes Ebnoutalib (Eintracht Frankfurt), Niclas Fuellkrug (Werder Bremen), Kai Havertz (Arsenal)