"I've been feeling very grateful, obviously, I have a little baby girl on the way," said Bloom, 43. "I'm so excited to have a little daddy's girl. I hope she's going to love me as much as I love her. That daddy girl thing and that love of your life feeling I think is right around there."
Fallon, who is the father of two girls -- Winnie, 7, and Franny, 5, -- replied, "No spoilers from me, but it really is love at first sight and it doesn't end. It's the best thing in the world."
Bloom said his 9-year-old son, Flynn, whom he shares with ex-wife Miranda Kerr, is "excited" to have a baby sister. Flynn also has two half-brothers: Hart, 2, and Myles, 10 months, who are Kerr's sons from her marriage to Evan Spiegel.
"I've got a 9-year-old boy. He's got a couple of other brothers but this is his first sister so he's excited too," Bloom said of Flynn. "It's exciting times."
The "Carnival Row" star also spoke about what he's been up to during coronavirus quarantine, including building some very impressive Lego cars with Flynn.
"This is hours of quarantine," Bloom said, showing off the dozens of figurines behind him. "I actually find it kind of reassuring...I got so into it."
"I was working a lot and I've found some real solace. I think it's a reset," he added of the pandemic. "Perhaps we all needed a chance to reflect on what's important and what we've been doing. I just hope that we can keep that thinking, that thinking can kind of continue on past and through once there are vaccines in place and people want to go about their lives."
Bloom also spoke to Hello! Magazine on Tuesday, revealing that he and Perry have decided on a hospital. However, the "Pirates of the Caribbean" star said they aren't opposed to other birthing options.
"We're taking it day by day," he said. "We have a hospital picked out, but every other option is on the table, because it needs to be. Katy's sister had home births and it's not something she’s afraid to do if she needs to. We just have to see how things pan out."
Perry first revealed she and Bloom were expecting in the music video for her song "Never Worn White" back in March. Toward the end of the love song, the "Firework" singer unveiled her growing baby bump.
Perry later confirmed the pregnancy through her Instagram Stories, saying, "Let's call it a reveal. I'm excited, we're excited and we're happy." She seemed to suggest they're expecting a summer baby, claiming the couple would be having a "jam packed summer."
Nearly a month later, Perry announced the couple is expecting a baby girl.
The pop star, who has been promoting her fifth studio album, "Smile," recently gave an update on her pregnancy journey.
"I'm really grateful for my body, and I have so much respect for women. And obviously going through this process is like, you know, you get a whole new viewpoint," Perry said on the Australian radio program "The Kyle and Jackie O Show" last month. "But everything is swollen. My hands are swollen. My feet are starting to swell. It's starting to get to that point."