How I Met Your Unfit Mother

Last night, Britney Spears appeared on one of my favorite trad sitcoms, “How I Met Your Mother” (7:30 p.m. Monday, CBS), a show that succeeds due to great, disciplined writing; one of the best ensembles on current television; and something I’ll call an uncommon internal logic system — more than half of the events on the show only make sense or are funny because of who these people are and what they have done since the series premiered. In short, there are few random moments on “How I Met Your Mother,” or things that a recent Harvard Lampoon staffer has had rattling around in his Ivy-cultivated mind for a few years and could hardly wait to deploy on his first gig, no matter how inappropriate.

I was ambivalent about Spears appearing on “Mother,” mainly because (a) I don’t like anything about her, but (b) she is notorious enough to gain exposure for a show deserving of attention but underperforming at Nielsen. Spears played a ditzy receptionist/intern at a dermatology clinic, where Ted Mosby (Josh Radnor) is getting a butterfly tattoo removed from his butt (a long story involving heavy booze and spite).