A few things...
1) Updating this post, Chicago and Kansas City both fielded their 100th players in the season openers. For KC, Matt Groenwald and Eddie Johnson will have to share the honor, as the Wizards were on 98 heading into the season and they both started the game. For the Fire, Calen Carr became their 100th player as he came on for Diego Gutierrez in the second half.
2) Brian Ching has 5 goals in two games. I don't believe anyone has done better in a two game span. However, when it comes to three consecutive games, he'll need a hat trick on Saturday at D.C. to equal the record.
Diego Serna scored 8 times in three games to close out the 2000 season, after the Fusion were already eliminated from playoff contention. He scored all 4 goals in a 4-1 home win over the Metros, then 1 goal at the Metros (in a 1-2 loss), and 3 more at D.C. in a 6-2 away win.
Maybe one D.C. hat trick deserves another?
Oh, and a few more players have scored 7 goals in three games:
2001-Alex Pineda Chacon
3) There is only MLS player to score in his only game in the league: Michael Butler.
4) I have made another MLS compilation, this one consisting of all RSL goals (at least the ones on tv) in their inaugural season. I think the song lyrics fit perfectly.