McAdams, who played the o.g. Regina George in 2004's Mean Girls, introduced Reneé Rapp’s "Not My Fault" performance and portrayed her own doppelganger in a sketch with Jacob Elordi.
This behind-the-scenes SNL video featuring Pete Davidson explains how brilliant minds at Saturday Night Live took a mere half-day to recreate a Staten Island-style Barbie Land.
SNL Five-Timer Christopher Walken appeared in the cold open and introduced musical guest Foo Fighters, recreating a classic Saturday Night Live moment.