Throughout season 1 and season 2 Elliot's and Ellyn's names are spelled incorrectly in the opening credits. Elliot's is spelled with two 't's ("Elliott"), and Ellyn's is spelled with a second 'e' instead of a 'y' ("Ellen"). "Ellyn" is not corrected until the first episode of season 3 (3.1 "Nancy's mom") and "Elliot", not until the fourth episode of season 3 (3.4 "new baby").
The early episodes in Season 1 featured scenes under the opening credits that were yet to be broadcast.