(written from a Production point of view)
Yeaggy was born Carlos Roberto Yaeggy in Guatemala in 1954.  In early 1982 he met actress Melody Thomas Scott on the set of The Young and the Restless and the two engaged.  A few months later their daughter Alexandra Danielle Yeaggy was born but the couple split in April 1984.  Following Yeaggy's death, Alexandra was adopted by Thomas Scott's third husband, producer Edward J. Scott whom she married in 1985.
Yeaggy served as examiner and executive committee member of the International Alliance of Theatrical and Stage Employees 706 Makeup Artists Union. He passed away on Sunday 30 March 1997 in Los Angeles, California at the age of 43 due to a heart attack. 
Following his uncredited work on Star Trek, Yeaggy worked for several years as makeup artist on the daily soaps Santa Barbara (1984-1989) and The Young and the Restless. For his work on Santa Barbara, he received Emmy Award nominations in the category Outstanding Achievement in Makeup for a Drama Series in 1987 and 1988, shared with Kim Adrissi and Dawn Marando. In 1989 he won an Emmy Award in this category as well as a Soap Opera Digest Award for his work on the soap and shared it with Dawn Marando and John Maldonado. 
Further work includes the crime drama American Me (1992, working with David Abbott, Tania McComas, Ken Diaz, Gloria Ponce, Jill Rockow, and Patricia Vecchio), the television drama Secrets (1992, starring Christopher Plummer and working with Linle White), the crime thriller The Harvest (1992, starring Miguel Ferrer), and the television drama Heartbeat (1993).
Also in the early 1990s, Yeaggy worked with David Abbott and Gilbert A. Mosko on the fantasy television series The Munsters Today, starring John Schuck, Lee Meriwether, and Jason Marsden. For this work, Yeaggy, Mosko and Abbott won an Emmy Award in the category Outstanding Achievement in Makeup in 1991. Yeaggy won his final Emmy Award in 1995 for his work on the daily soap The Guiding Light.
More credits as makeup artist include the final season of the drama series Reasonable Doubts (1992-1993, working with Audrey L. Anzures) and the second season of the comic adaptation Lois & Clark: The New Adventures of Superman (1994-1995, starring Teri Hatcher and K Callan and working with Rita Bellissimo, Cheri Ruff, and Susan Zietlow-Maust).
Among his last known work are the television movie Cutty Whitman (1996, with Richard Libertini), the sport drama Jerry Maguire (1996), the mystery thriller Shadow of Doubt (1998, with Pancho Demmings, Richard Penn, Tony Plana, and Granville Ames), and the seventh season of the drama series Beverly Hills, 90210 (1996-1997). The episode "Mother's Day", directed by Chip Chalmers, featured the end title sequence "in loving memory of our dear friend Carlos Yeaggy" to remember his death.