The "Toy Story" actor reveals he has crossed paths with Tiffany twice to date, but accidentally snubbed her on both occasions.
Tim admits part of the problem is his shy nature at public events, and adds he didn't expect the "Girls Trip" star to be so tall.
"Tiffany Haddish, I think, is real funny," he told U.S. show "The Talk". "Now, I've run into her twice and I'm kind of an introvert, so I don't really make eye contact when I'm out, it's just one of those things."
"She's tried to say hello, and (first) it was at the Golden Globes. (She said), 'Hi, Tim!' and before she could say her name, I (held up my hands) and walked away. I get in the car and someone said, 'That was Tiffany Haddish...' "
"She's taller than you might imagine. I said, 'Oh, God, that's horrible'. I didn't say hi. I felt like an idiot."
Tim then came across Tiffany while volunteering to feed the homeless, but he again missed his opportunity to heap praise on her, and ended up mistaking her for a woman in need when she was just joking around.
"We were in the soup kitchen, all the comics get together to feed the hungry on Christmas Day or Thanksgiving, and she was there," he recalled. "Of course, I was busy, and then the owner... says, 'We're gonna give out money to the homeless.' "
"She (Tiffany) walks by and goes, 'Hey, how 'bout money for me?' I didn't recognise her so I gave her money!"
"Somebody said, 'Why did you give Tiffany money?' I go, 'Oh, God, was that her again?' "
Tiffany has yet to react to Tim's TV confession.