I was sitting here thinking about how many shows have characters of the same name. There is probably already a thread like this on here, I searched for it but I couldn't find it. If you feel this needs to be moved, please do so, thanks!
I have thought of several characters with the same name from different shows. Here are a few.

Niles-Frasier and The Nanny
Roz-Frasier and Night Court
DJ-Roseanne and Full House
Martin-Martin and Frasier
Chrissy-Three's Company and Growing Pains
Alex-Family Ties, Full House, SVU, Taxi
Nicky-Full House and Fresh Prince
Olivia-The Cosby Show and SVU
Thelma-Good Times and Amen
Barbara-One Day at a Time and Empty Nest
Christine-Night Court and New Adventures of Old Christine
Tony-Taxi and Who's the Boss?
Jim-Taxi and According to Jim
Richie-Dick Van Dyke and Happy Days

Please feel free to post your own. I will post more later when I think of more.

eric forman that 70s show and house

I just thought of another.

Hank Lawson-Dr. Quinn and Royal Pains

Samantha-Bewitched and Who's The Boss

Buffy- 'Family Affair' and 'Buffy the Vampire Slayer'

Bobby-'The Brady Bunch' and 'Dallas'

Laura-'Little House on the Prairie', 'The Dick Van Dyke Show' and 'Family Matters'

Ralph-'The Honeymooners' and 'Happy Days'

Mary-'The Mary Tyler Moore Show' and 'Little House on the Prairie'

Mike Nelson - Sea Hunt and Mystery Science Theatre 3000

Wilton Parmenter--F Troop and The New Gidget

Theodore J. Mooney--Dennis The Menace and The Lucy Show

Janos Skorzeny--Kolchak: The Night Stalker and Werewolf

Uncle Jesse-'Full House' and 'Dukes of Hazzard'

Drew Carey -- Matlock* and The Drew Carey Show
(*yes, Matlock actually had a one-shot character named Drew Carey!)

Darby- Minor Adjustment and Second Noah
Rose - 227, Golden Girls/Palace and Little House on the Prairie
Harriet(te)-Family Matters, Small Wonder, Little House on the Prairie

I know this thread is old but I just thought of one and had to add it.

Rachel-Friends, Glee, Family Matters

J.R. (Jones of Barnaby Jones and Ewing of Dallas)

Tootie- Facts of Life, Fairly OddParents

Archie - Archie Bunker , All in the family & Archie Andrews ,The Archies

Fred - Fred G .Sanford ,Sanford and Son & Fred Flintstone ,The Flintstones

Jason- Jason Walton ,The Waltons & Jason Bolt , Here come the brides

George (The Jetsons, The Jeffersons, and Seinfeld)

Sabrina - Sabrina Spellman - Sabrina the teenage witch & Sabrina from Charlie's Angels

Oliver -Oliver Wendell Douglas ,Green Acres & Oliver , cousin on the Brady Bunch

Eddie -Eddie Haskell, Leave it to Beaver & Eddie Munster, The Munsters

I have a lot.

Judy: Friends and How I Met Your Mother
Jack: Friends and 30 Rock
Elizabeth: Friends and 30 Rock (real name of Liz)
Frank: Friends and 30 Rock
Carol: Friends, 30 Rock, and How I Met Your Mother
JD: Scrubs and 30 Rock
Ben: Friends and Parks and Recreation (2 on that show, actually)
Jerry: Parks and Recreation and Seineld (though, Jerry Gergich might not count since that's not his real name)
Gar(r)y: Parks and Recreation (real name of Jerry) and How I Met Your Mother (might not count since they're spelt different)
Tracy: 30 Rock and How I Met Your Mother
George: Seinfeld and How I Met Your Mother (The Captain)
Penny: Big Bang Theory and How I Met Your Mother
James: 30 Rock (Toofer) and How I Met Your Mother
Quinn: Portlandia and How I Met Your Mother
Sandy: Friends and How I Met Your Mother
Don: How I Met Your Mother and Parks and Recreation
Becky: How I Met Your Mother, Roseanne, and Full House
Janice: How I Met Your Mother and Friends
Adam: How I Met Your Mother (Punchy) and Family Guy
Sam: Portlandia and How I Met Your Mother

Arnold Horshak - Welcome back Kotter & Arnold Ziffel - Green Acres

Julie Kotter - Welcome back Kotter & Julie Cooper Hovath - One day at a time

Okay I just realized that there are more that I need to add.
I already added Rachel as characters on Friends, Family Matters and Glee but there was also a Rachel on Boy Meets World, she was on in the later seasons.

Also there was a Jennifer on Family Ties, WKRP in Cincinnati, and Home Improvement. There were two minor characters named Jennifer on Full House who were friends with Stephanie.

Jack is also a pretty popular character name. There was a Jack on Friends, Boy Meets World, and Three's Company.

Also there was a Jennifer on Family Ties, WKRP in Cincinnati, and Home Improvement. There were two minor characters named Jennifer on Full House who were friends with Stephanie.


And of course there was Jennifer Hart (wife of Jonathan) on Hart to Hart!

Frasier fans would be familiar with Martin Crane. But that wasn't the first character with that name, Martin Mull played Martin Crane in Domestic Life from 1984. He was on Johnny Carson last night promoting it, saying it was a parody of sitcoms.

Alex: "Wizards of Waverly Place" and "The Donna Reed Show."

Alex: "Wizards of Waverly Place" and "The Donna Reed Show."

There was also Alex Lambert on Wings.

There was also Alex Lambert on Wings.

And Alex Mack of The Secret World of Alex Mack on Nickelodeon.

Bumping this up: Mike (Hammer on Mike Hammer, Brady on The Brady Bunch, and Stone on The Streets of San Francisco).

Andy

Andy Taylor
Andy Dwyer
Andy Travis

Jason- Jason Walton ,The Waltons & Jason Bolt , Here come the brides

Bumping this up: Jason Colby (the late, great Charlton Heston) on The Colbys (ill-fated 1985-87 spinoff of O-R ABC Dynasty)

Carol= Growing Pains, Empty Nest, Step by Step, The Brady Bunch
Kate= Silver Spoons, Alf , Kate & Allie, Castle, Dear John, Family
Harry= Night Court, Empty Nest
Kevin= The Wonder Years, Mr.Belvedere This is Us, The Office, Joan of Acradia
Joey= Gimmie A Break, Friends, Blossom, Melissa & Joey, Full House, My Two Dads
John= Dear John, Hearts Afire, NYPD Blue, Life in Pieces
Jack= The Wonder Years, Will & Grace, This is Us
Lauren Miller= Family Ties & Still Standing
Brian= Alf,Still Standing, Wings
Amy=The Big Bang Theory, Judging Amy, It's A Living, Brooklyn Nine Nine, Superstore
George= Webster ,Mr. Belvedere, Young Sheldon, The Jeffersons, Boy Meets World, Suburagtory
Zack= Saved by the Bell, The Suite Life of Zack & Cody
Lily= How I Met Your Mother, The Munsters
Karen= Step by Step, Will & Grace, Psych
Rory= Gilmore Girls, 8 Simple Rules
Dana= Step by Step, According to Jim
Mark= The Hogan Family, Step by Step, Home Improvement, One Day at a time, Hanging with Mr. Cooper
Fran= The Nanny, Living with Fran
Cody= Step by Step, The Suite Life of Zack & Cody
Kelly= Saved by the Bell, Beverly Hills 90210, Married with Children, Coach, The Office
Darlene= Head of the Class, Roseanne
Charlie= Head of the Class, Two & Half Men, Good Luck Charlie, Numbers
Alex= Head of the Class, Modern Family, One day at a time, Supergirl
Gloria= All in the Family, Modern Family
Angela= Who's the Boss, My So Called Life, The Office, American Housewife
All= Step by Step, Home Improvement, Married with Children, Unforgettable
Alan= Head of the Class, Two & Half Men, Boston Legal
Mike= Growing Pains, Mike & Molly, Suits, The Middle, Last Man Standing
Barbara= One Day at A Time, Empty Nest
Max= One Day at a time, 2 Broke Girls
Earl= My Name is Earl, 2 Broke Girls
Randy= Home Improvement, My Name is Earl
Katie= Gimmie A Break, Benson, American Housewife
Sam= Cheers, One Day at a Time, Different Strokes, Supernatural
Maggie= Growing Pains, Gimmie a Break, Different Strokes
Dan= Roseanne, Night Court, Gossip Girl
Blair= The Facts of Life, Gossip Girl
Jackie= Roseanne, Too Close for Comfort
Vinnie= Doogie Howser, Welcome Back Kotter
Katherine= Webster, Doogie Howser, A Million Little Things
Stephaine= Newhart, Full House
Michael= My Two Dads, The Good Place, The Office, The Hogan Family, Newhart, Burn Notice, Thritysomething
David= The Hogan Family, Doogie Howser
Willie= Alf, The Hogan Family
Greg= The Brady Bunch, American Housewife ,Yes Dear, Life in Pieces, Dharma & Greg
Christine= Coach, Yes Dear
Oliver= American Housewife, Hannah Montana
Oscar= The Office, The Odd Couple
Dwayne= One Day at a Time, A Different World, What's Happening
Malcolm= Malcolm in the Middle, Malcolm & Eddie
Harvey= Sabrina the Teenage Witch, Suits
Brenda= 227, Beverly Hills 90210
Morgan= Boy Meets World, Sabrina the Teenage Witch
Adam= The Goldbergs, Parenthood, Dynasty, Man with A Plan
Jimmy= Speechless, Yes Dear
Maya= Speechless, Girl Meets World
Eric= Head of the Class, Boy Meets World, 7th Heaven
Carrie= The King of Queens , Sex & the City, Unforgettable
Jamie= Mad About You, Small Wonder, Blue Bloods
Frank= Shameless, Step by Step, Blue Bloods, Hill Street Blues
Vanessa= The Cosby Show, Small Wonder, Last Man Standing, Hanging with Mr. Cooper
Barney= How I Met Your Mother, The Flintstones
Mary= 227, 7th Heaven, Young Sheldon
Lucy= 7th Heaven, I Love Lucy, Life with Lucy
Sarah= Parenthood, Jag, Head of the Class
Spencer= ICarly, Pretty Little Liars
Nora= Brothers & Sisters , The Naked Truth
Jo= The Facts of Life, CSI NY
Woody= The Suite Life on Deck, Cheers
Ted= How I Met Your Mother, The Mary Tyler Moore Show
Lou= Bunk'd, Hawaii 5-0, The Mary Tyler Moore Show
Taylor= Evening Shade, American Housewife
Molly= Evening Shade, Mike & Molly
Emily= Gilmore Girls, Empty Nest, Evening Shade
Paul= Mad About You, 8 Simple Rules
Fiona= Shameless, Burn Notice
Andy= Family Ties, NYPD Blue
Meredith= Grey's Anatomy, The Office
Samantha= Gimmie a Break, Sex & the City, Life in Pieces
Carl= Family Matters, Mike & Molly
Gary= Dallas, A Million Little Things
Danny= Hawaii 5-0, Blue Bloods, Full House
Elliot= Scrubs, Thritysomething
Carla= Cheers, Scrubs
Elizabeth= The Blacklist, Madam Sec.
Henry= Madam Sec. Too Close for Comfort, Psych
Richard= Gilmore Girls, Castle
Erin= Blue Bloods, Chicago PD
Jason= Growing Pains, Bull, The Game
Shawn= Psych, Boy Meets World
Monica= Friends, Touched by and Angel
Tess= Touched by and Angel, This is Us
Bridget= Bridget Loves Bernie, 8 Simple Rules
Pam= The Office, Martin
Caroline= 2 Broke Girls, Caroline in the City
Annie= 7th Heaven, One Day at a Time, This is Us
Cindy= The Brady Bunch, Three's Company
JJ= Speechless, Good Times
Nicole= My Two Dads, Hanging with Mr. Cooper
Howard= The Big Bang Theory, Happy Days, Hill Street Blue
Heather= Mr. Belvedere, Life in Pieces
Joan= Joan of Arcadia, Life in Pieces, Small Wonder
Teddy= Good Luck Charlie, Man with A Plan
Ben= Growing Pains, Baby Daddy
Riley= Girl Meets World, Baby Daddy, So Little Time
Dylan= Beverly Hills 90210, Speechless
Jake= Brooklyn Nine Nine, Two and a Half Men
Ray= Speechless, Sister Sister
Claire= Modern Family, My Wife and Kids
Cate= 8 Simple Rules, Life Unexpected
Sydney= Alias, Providence
Bonnie= Small Wonder, Mom
Helen= Wings, The Jeffersons Three's Company
Donna= Suits, Beverly Hills 90210, That 70's Show
Lynn=Mr Belvedere, Alf
Phil= Modern Family, The Fresh Prince of Bel Air
Will= The Fresh Prince of Bel Air, Single Parents, Will & Grace
Lisa= The Simpsons, Saved by the Bell, Sister Sister
Alexis= Dynasty, Castle
Jess= New Girl, Gilmore Girls
Jessica= Soap, Fresh off the Boat
Luke= Gilmore Girls, Modern Family
Julia= Parenthood, Designing Women
Anthony= Blossom, Designing Women
Phoebe= Charmed, Friends
Kittty= That 70's Show, Brothers & Sisters
Jan= The Brady Bunch, It's A Living
Laverne= Empty Nest, Laverne & Shirley
Jill= Home Improvement, Mom
Jane= Rizzoli & Isles, Jane the Virgin
Tia= Sister Sister, All of Us
Rebecca= Cheers. This is Us
Bernadette= The Big Bang Theory, Head of the Class


and for last names = Tanner Full House & Alf
Hogan= Hogan's Heroes & The Hogan Family

Peter Brady - The Brady bunch and Peter Newman - Foley Square

Barbara Douglas - My three sons - Barbara Cooper- Royer - One day at a time

Sgt. Vince Carter-Gomer Pyle
Sgt. Andrew Carter-Hogans Heroes
J.R. Jones-Barnaby Jones
J.R. Ewing-Dallas
Jethro Gibbs-N.C.I.S.
Jethro Bodine-The Beverly Hillbillies

Carla

Cheers

Scrubs