Quarterback Jimmy Clausen most recently wore #7 for the Irish.
I think if you are referring to the shirt where you see the number 12 on the jersey of the player in the tunnel, then the number 12 is referring to the fans or the 12th man as they have been called.
Also QB Brady Quinn from 2003-06, as well as:
Glen "Judge" Carberry (1920-22)
Charles "Chile" Walsh (1925-27)
Al "Bud" Gebert (1928-29)
Joe Sheeketski (1930-32)
Ed Sadowski (1936)
John Creevey (1942-46)
Frank Paterra (1951-52)
Dick Selcer (1956-58)
Mike Earley (1966)
Ed Devine (1968)
Brian Lewallen (1968-69)
Darryll Dewan (1970-72)
Randy Harrison (1974-78)
Scott Grooms (1980-84)
Brian Whelan (1981)
Rick Ebert (1988)
Adrian Jarrell (1989-93)
Mike Perona (1995-96)
Deveron Harper (1996-99)
Matt LoVecchio (2000-01)
Quarterback Jimmy Clausen most recently wore #7 for the Irish.
Paul Hornung
sharply
Julian
Tyler
George Gipp wore the number 66 while he played at Notre Dame.
Paul Hornung
Tom gate wood
Joe Montana wore #3 during his time at Note Dame. He attended Notre Dame from 1974 to 1978.
Brady Quinn wore 10 at Notre Dame when he was quarterback there.
paul hornung
The most famous was Tony Rice a Quarterback in 1988 for the national championship team.
Assuming you're asking about the football team, two players wore #5 in 2010: Armando Allen (RB) on offense, and Manti Te'o (MLB) on defense.
Marc Edwards (Fullback)Grant Irons (Defensive End)
Jerome Bettis did not claim a major in college. He did attend college at Notre Dame but did not graduate. He took classes in history, philosophy, marketing and business.