Jeff the Doorman has an affinity for frogs. He is the afterlife gatekeeper who controls the doorway connecting the afterlife with Earth and becomes one of the show's most memorable supporting figures.
Jeff's fondness for frogs is presented as a defining personal detail rather than a major plot mystery. His frog enthusiasm gives Michael and the other characters a simple way to understand and connect with him, despite Jeff's enormous age and his long, uneventful work shift.
The frog detail also leads to one of Michael's more thoughtful gestures. Michael remembers Jeff's interest and gives him a frog-themed gift, helping demonstrate that Michael is becoming more attentive to other people's preferences. Viewers sometimes confuse Jeff's affinity with the animals involved in the show's many fantastical settings, but the canonical answer is frogs.
Jeff is played by Mike O'Malley. He works in the Neutral Zone and guards the passage to Earth, making him important to the characters' attempts to revisit the human world.