Generation 0
Who knew that selecting pitcher Bobby Shantz in the 21st round of the 1961 expansion draft would have so many ripples through the early years of the Houston franchise, especially since he only threw three games for the Colt .45's? Shantz was a three time All-Star, five time Gold Glove winner, and one time MVP before coming to Houston as a 36 year old. He started three games for Houston, going 1-1 with a 1.31 ERA before being traded to St. Louis for John Anderson and Carl Warwick. Shantz was good for .6 WAR in those three games.
Generation 1
John Anderson was what we would today call a AAAA relief pitcher. As a 32 year old he had appeared in all of 14 major league games before coming to Houston. Anderson would throw 10 more forgettable games for the Colt's, putting up a 5.09 ERA and never appeared in the majors again. His performance netted Houston 0.0 WAR.
Carl Warwick was a 25 year old outfielder at the time of the trade. He played in 280 games for Houston over two seasons, hitting .257/.315/.373 for a nearly league average OPS+ of 97 with 23 home runs, good for 1.8 WAR. Warwick was traded back to St. Louis before the 1964 season for Jim Beauchamp and Chuck Taylor.
Generation 2
Jim Beauchamp was coming off a breakout AA season, .337/.394/.625 with 31 homers, when he was traded to the Houston organization. He had another monster season for Houston's AAA franchise in Oklahoma City before being called up at the end of the 1964 season. He hit just .176/.244/.259 for Houston in 119 plate appearances before being traded, along with starter Ken Johnson, to the Milwaukee Braves for Lee Maye in May of 1965. Beauchamp was good for (-0.9) WAR during that stint and never lived up to the potential he showed in the minors.
Chuck Taylor was a promising minor league starter when he came to the Houston organization, but struggled mightily for two seasons at the AA and AAA level after the trade. He never appeared in the majors for Houston, though he did end up with an eight year career as a pretty decent reliever after being traded by Houston, along with Hal Woodeshick, back to St. Louis for Mike Cuellar and Ron Taylor in June of 1965. Interestingly enough, he and Beauchamp would be traded together again by St. Louis in 1971 to the Mets.
Generation 3
Here's where it starts getting fun to keep up with. Stay with me.
Lee Maye was a solid outfielder who had led the National League in double the prior season when he came to Houston. He spent two seasons with the Astros, hitting .268/.302/.380 (a 97 OPS+) with 12 homers and 11 triples but playing questionable defense, good for just .1 WAR. Maye was traded before the 1967 season, along with Ken Retzer, to Cleveland for Doc Edwards, Jim Landis, and Jim Weaver.
Before coming to Houston, Ron Taylor was a below average 27 year old relief pitcher and his one and a half seasons with the Astros didn't prove otherwise. He appeared in 68 games for Houston going 3-8 with a 6.03 ERA, good for (-2.1) WAR before being purchased by the Mets prior to the 1967 season. He did have a nice four year run with New York, though.
Mike Cuellar was a pretty good starter for the Astros, going 37-36 with a 2.74 ERA and making the All-Star team in 1967. In December of 1968 Mike was traded to Baltimore along with minor leaguers Elijah Johnson and Enzo Hernandez for John Mason and Curt Blefary. Cuellar would go on to win the AL Cy Young in 1969, finish fourth in 1970, and make the All-Star team four times for the Orioles.
Generation 4
Jim "Fluff" Weaver spent one year as a starter for Houston's AAA club in Oklahoma City, where he was 12-7 with a 2.70 ERA. He was traded in August of 1967 to the Angels for a player to be named later. That PTBNL ended up being shortstop Hector Torres.
Jim Landis was a former Gold Glove center fielder (defensive metrics introduced since that time suggest he wasn't a very good fielder) who put up good walk rates back when that sort of thing wasn't really recognized as important. In 50 games for Houston in 1967 Landis hit .252/.341/.364, which was actually good for a 106 OPS+, but his defense dragged him down to a (-0.1) WAR. In June of 1967 Landis was traded to Detroit for Larry Sherry.
Doc Edwards, despite the cool gunslinger name, was a former major league catcher who, at this point in his career, was used for AAA depth. In his one season with Houston's farm, Edwards hit .219/.271/.285. Following that season he was drafted by the Phillies in the minor league draft. As of 2012, Edwards was managing the San Angelo Colts of the independent North American League.
Curt Blefary was a former rookie of the year first baseman before arriving in Houston. He spent what turned out to be his last truly productive season with the Astros in 1969, when he hit .253/.347/.393 (a 109 OPS+) with 12 home runs, netting him 1.6 WAR. Blefary was traded to the Yankees, one year to the day (December 4th each year) he became an Astro, for Joe Pepitone.
John Mason was a career minor league IF/OF. He spent four years with Oklahoma City, with his best season coming in 1971 when he hit .292/.351/.353, before hanging up his spikes.
Generation 5
Joe Pepitone was a former All-Star and Gold Glove winning 1B/OF (another who didn't seem to warrant the award based on modern defensive metrics) before coming to Houston. In half a season with the Astros, Pepi hit .251/.298/.470 with 14 home runs, good for 0.1 WAR before being purchased by the Cubs in July of 1970.
Larry Sherry was a decent relief pitcher who, in 29 games for Houston in 1967 was 1-2 with six saves and a 4.87 ERA. He was released by Houston just before Opening Day in 1968.
Hector Torres ended up being a light-hitting shortstop in his three seasons with Houston. In 193 games from 1968-1970, Torres hit .218/.251/.260, earning (-2.1) WAR before being traded to the Cubs for Roger Metzger. Houston would pick Torres up again for the 1973 season, when he put up a (-15) OPS+ in 79 plate appearances.
Generation 6
The final descendant of Shantz in this trade tree, Roger Metzger was a slick fielding, non-hitting shortstop who anchored the Astros infield from 1971-1978. In 1,021 games for Houston, Metzger hit .229/.291/.291 with 64 stolen bases, totaling 4.1 WAR and picking up a Gold Glove in 1973 along the way. Metzger also led the NL in triples in 1971 and 1973. Roger was purchased by the Giants in 1978.
So, there you have it. The story of how an expansion-drafted 36 year old pitcher who appeared in just three games for Houston turned into 16 players, spanning 16 seasons, for the young organization.