Brian

From the Super Mario Wiki

Brian is a character in the Game Boy Color version of Mario Tennis. It appears as if he and his daughter both like the color green, since they both wear shirts and pants that are green. He is ranked 4th in Senior class. He is an all-around player.

Mario Tennis Series Playable Characters
Mario's Tennis
Donkey Kong Jr. · Koopa Troopa · Luigi · Mario · Princess Toadstool · Toad · Yoshi
Mario Tennis (Nintendo 64)
Baby Mario · Birdo · Boo · Bowser · Daisy · Donkey Kong · Donkey Kong Jr. · Luigi · Mario · Paratroopa · Peach · Shy Guy · Toad · Waluigi · Wario · Yoshi
Mario Tennis (Game Boy Color)
Alex · Allie · A. Coz · Baby Mario · Beth · Bob · Bowser · Brian · B. Coz · Curt · Donkey Kong · Elden · Emily · Fay · Harry · Joy · Kate · Luigi · Mario · Mark · Nina · Pam · Peach · Sammi · Sean · Spike · Waluigi · Wario · Yoshi
Mario Power Tennis (Nintendo GameCube)
Boo · Bowser · Bowser Jr. · Daisy · Diddy Kong · Donkey Kong · Fly Guy · Koopa Troopa · Luigi · Mario · Paratroopa · Peach · Petey Piranha · Shy Guy · Waluigi · Wario · Wiggler · Yoshi
Mario Power Tennis (Game Boy Advance)
Barb · Bowser · Chad · Chas · Chris · Donkey Kong · Dweezil · Elroy · Emi · Flit · Gary · Jet · Kyle · Kyoko · Linda · Luigi · Mario · Mason · Max (Clay) · Meg · Mel · Micki · Mynx · Paula · Princess Peach · Roy · Sasha · Sass · Shawn · Sheri · Skipper · Sophia · Sylvia · Tina (Ace) · Tori · Waluigi · Whisker · Willy

Human Characters
Humans in the Mario series A. Coz | Alex | Allie | Azalea | B. Coz | Baby Daisy | Baby Luigi | Baby Mario | Baby Peach | Baby Wario | Bean | Beth | Bird | Bob | Brian | Booster | Buzz | Charlie | Curator | Curt | Elden | Elroy | Emi | Emily | Fay | Flit | Foreman Spike | Gary | Grace | Harry (Mario Golf) | Harry (Mario Tennis) | Helen | Isaac Newton | Joe | Joy | Kate | Ken | Kid | King Fret | Kyoko | Lady Timpani | Lisa | Mama Mario | Mario | Mason | Max | Luigi | Mark | Mushroom King | Napple | Nina | Onnanoko | Oyaji | Pam | Papa | Paula | Pauline | Plum | Prince Pine | Princess Daisy | Princess Peach | Powert | Professor Elvin Gadd | Putts | Rosalina | Rozary | Sasha | Sean | Sherry | Sonny | Spike | Stanley the Bugman | Steve | Thread | Tina | Tori | Waluigi | Wario | Whisker
Humans in the Wario series 5-Volt | 9-Volt | 18-Volt | Ana's Crew | Ashley | Bridget the Baker | Captain Syrup | Carpaccio | Count Cannoli | Dr. Crygor | Dr. Payne | The Dinosaurs | Jimmy P. | Jimmy T. | Kat and Ana | Mona | Mad Scienstein | Penny Crygor | Sal Out | Sammy Rai | Shop Manager Iwata | Young Cricket and Master Mantis
Humans from other series Captain Falcon | Colonel Roy Campbell | Dr. Eggman | Eggman Nega | Ike | Little Mac | Lucas | Marth | Mei Ling | Ness | Otacon | Pokémon Trainer | Roy | Samus Aran | Solid Snake
Humans in other media Captain Falcon | Ali Mustafa | Alligator Dundee | Alyssa Milano | Angelica | Anthony Scapelli | Aunt Luigeena | Aunt Maria | Blanka | Bones | Brian Bonsall | Brutius Maximus Grouchimus | Butterfingers | Captain Abidab | Captain Clump | Captain Lou Albano | Chief Quimby | Cher | Chun-Li | Cowboy Jed | Crab | Crimewave Clyde | Cutter | Cybele | Cyndi Lauper | Daniella | David Horowitz | Dealin' Delbert | Dhalsim | Doc Freud | Dr. Frankenstein | Dr. Light | Dr. Nerdnick | Dr. Sheldon | Dr. Sigmund Fruitcake | Dr. T. Garden | Dr. Toby | Dr. Wily | Edison | Einstein | Elvin Parsley | Elvira | Elvis Presley | Erik, Baleog and Olaf | Ernie Hudson | Fire God | Flab Boys | Friendly Floyd | Gondolier | Gramma Toadstool | Grandma Mario | Grandma Mia | Grandpapa | Ellie Mae | Harry Blackstone Jr. | Helmut Kohl | Hercufleas | Herlock Solmes | Herman | Herman Smirch | Hildy | Imperial Poobah | Indiana Joe | Inspector Gadget | James Blonde | Jason Bateman | Jodie | Joe and Mac | Joliet | Junior | Junior's Parents | Kid Klown | King James | King Mushroomkhamen | King Toadstool | King Windbag | Klösn | Liz | Luigeena | Luigi's Girlfriend | Lyle Alzado | Madam AGoGo | Marco Polo's Plumbers | Marianne | Marilyn | Mario Joe and Luigi Bob | Mark Twang | Max Milliplatt | Mayor of New York City | Mikhail S. Gorbachev | Milli Vanilli | Misaki | Miss Endless | Miss O'Hara | Mervin the Magician | Mighty Plumber | Mona | Mouth of the River | Mr. Gibbel | Mr. Levison | Mr. President | Mrs. Gammliss | Mrs. Periwinkle | Mrs. President | Mugga | Netty | Nicole Eggert | Oogtar | Pam Matteson | Patty | Patty (Saturday Supercade) | Patty's Parents | Pietro | Prince Mushroomkhamen | Prince Pompadour | Queen Mushroomkhamen | Queen Rotunda | Rob Stone | Romano | Romano and Joliet's Fathers | Rowdy Roddy Piper | Roxanne | Salvador Drainado | Sam Shalam | Santa Claus | Secret Agent N | Sergeant Kooperman | Sgt. Slaughter | Shabba-Doo | Submarine Captain | Sultan Pasbah | Susanna Ross | Tawny Tyler | Ted Bull | The Old Psychic Lady with the Evil Eye Who Reads Fortunes and Knows Everything Before it Happens | Tommy Lasagna | Vampa White | Waldo the Wizard | Young McDonald | Zangief | Zero