I know him from The Boondock Saints; and Spider-Man; and Fireflies in the Garden; and Shadow of the Vampire; and Cirque du Freak: The Vampire's Assistant; and The Grand Budapest Hotel; and The Fault in Our Stars; and John Wick; and Odd Thomas; and voice work in Finding Nemo; and Fantastic Mr. Fox. And I've surely seen him in things I've forgotten.
I know him best from The O.C., but there's also Lost, and Once Upon a Time, and Don't Be Afraid of the Dark, and Captain America: The Winter Soldier, and I've surely seen him in other things that I don't specifically remember.
I know him from Wings; and Eyes; and some voice work.
I mainly know him from Cheers, of course. But there's also 3 Men and a Baby (and its sequel); and Ink; and Mumford; and Becker; and The Good Place; and a few episodes of The Orville; and probably things I've forgotten.
I know him from There's Something About Mary; and The Cape; and season 6 of Community; and The Quick and the Dead; and Pitch Black; and an ep of Speechless; and an ep of Fresh off the Boat; and a minor role in Nope; and some voice work. And surely I've seen or heard him in numerous other roles that I don't really remember.
I know him from Do the Right Thing; and The Stand; and Evening Shade; and Bubba Ho-tep; and possibly some other things. (Or not.)
I know from Return of the Jedi (Wicket); and Willow; and Prince Caspian & The Voyage of the Dawn Treader (Reepicheep); and The Silver Chair (Glimfeather); and The 10th Kingdom (Acorn); and Leprechaun; and an episode of Doctor Who (Porridge); and the Harry Potter movies (Filius Flitwick, et al.).
He was decent in Honey, I Shrunk the Kids: The TV Show, and a too-brief role in Heroes, and Terminator: The Sarah Connor Chronicles, and The Secret Circle.
de Lancie, John
I know him best as "Q" from Star Trek: The Next Generation, Deep Space Nine, and Voyager. Also there was The Hand That Rocks the Cradle; and an episode of Torchwood: Miracle Day; and some voice work.
I know him from The Muppet Movie; and Burke's Law; and a minor role in Blazing Saddles. But mainly I know him for his voice work.
De Niro, Robert
I know him from Taxi Driver; and Goodfellas (which I don't remember); and Mary Shelley's Frankenstein; and Hide and Seek; and Stardust; and Silver Linings Playbook; a small role in American Hustle; and Jackie Brown; and Limitless; and Joker; and Brazil; and possibly some other stuff.
Mainly know him from Buffy the Vampire Slayer and Angel. But I've also seen him in a few eps of How I Met Your Mother; and Dollhouse; and Grimm. And he voiced Mirror Master in an ep of Justice League and Justice League: Doom; and Dr. Quintum in All-Star Superman; and Nigel Taylor in Tarzan & Jane.
I know him from The Flash; and Becker; and Boy Meets World; and Invisible Sister. And he voiced Nick Fury in The Avengers: Earth's Mightiest Heroes. He was also in the band "Hepcat," though I only know like one of their songs, I think.
I know him from Taxi; and Romancing the Stone; and The Jewel of the Nile; and Batman Returns; and L.A. Confidential; and Mars Attacks!; and Anything Else; and When in Rome; and a cameo in Austin Powers in Goldmember; and Big Fish; and Jumanji: The Next Level; and voice work in Hercules; and Last Action Hero; and Space Jam; and The Lorax; and surely lots of things I don't remember so well. Also a commercial for Nespresso.
Um, he was on Growing Pains for awhile. And there was Titanic; and The Beach; and Inception; and The Quick and the Dead; and The Aviator; and Romeo + Juliet; and Django Unchained; and Shutter Island. And I think he was in a Bubble Yum commercial I saw on one of my old VHS tapes and I was all, "OMG, that's Leonardo DiCaprio!" Or whatever.
I know him from Pitch Black; and The Fast and the Furious; and he voiced Groot in Guardians of the Galaxy (and in Ralph Breaks the Internet); and the title character in The Iron Giant.
I know him from Singles; and Wild Things; and There's Something About Mary; and Herbie: Fully Loaded; and Wayward Pines. I've probably seen him in things I've forgotten him from, and I'd like to see more of his work.
I know him from Elf; and Threshold; and Penelope; and Prince Caspian; and Knights of Badassdom; and Pixels; and Avengers: Infinity War; and X-Men: Days of Future Past; and voice work in The Croods: A New Age.
Mainly think of him as the title character in Johnny Bago, which was pretty cool. Also Eddie in Lenny. I've probably seen him in some other stuff I don't really remember. I know I saw at least a bit of the series Cover Me. Shame I can't find any good links for him. He's someone who, if I'd seen more of his work, I might well consider a favorite...
I know him from Partners, and The O.C., and Nancy Drew, and an episode of Elementary, and he voiced the title character in Hercules (and its spin-offs). And I must have seen or heard him in other things I don't specifically remember him from.
Mainly know him as Worf from Star Trek: The Next Generation and Deep Space Nine, of course. And Star Trek VI, in which he played an ancestor of Worf's. And he's been in several episodes of Castle; and The Santa Clause 2 and 3. Also various voice work.
I know him from Beauty and the Beast; and at least a couple eps of The Wizard; and several eps of Picket Fences; and The Cutting Edge; and an episode of Angel; and probably various other stuff.
Downey Jr., Robert
I know him from the Iron Man movies, and Kiss Kiss Bang Bang, and Good Night, and Good Luck., and Sherlock Holmes, and A Scanner Darkly, and Weird Science, and Gothika; and The Soloist; and Heart and Souls; and Natural Born Killers; and Soapdish.
Mainly know him from The X-Files. There's also Aquarius, and Evolution. I think that's all I've seen.
I know him best from Evening Shade. But there's also The Muppet Movie; and Dark Night of the Scarecrow; and Dick Tracy; and O Brother Where Art Thou?; and several eps of Everybody Loves Raymond; and Mr. St. Nick; and When a Stranger Calls; and probably some other stuff I've forgotten. Also voice work as the narrator of Now & Again; and Francis Griffin in a few eps of Family Guy.