WordNet (r) 3.0 (2006):

creep in
    v 1: enter surreptitiously; "He sneaked in under cover of
         darkness"; "In this essay, the author's personal feelings
         creep in" [syn: sneak in, creep in]

Moby Thesaurus II by Grady Ward, 1.0:

98 Moby Thesaurus words for "creep in":
   admit, affiliate, affiliate with, associate, barge in, be admitted,
   break in, break in upon, breeze in, burst in, bust in, butt in,
   charge in, combine, come barging in, come between,
   come breezing in, come busting in, come in, come into, crash,
   crash in, crash the gates, cross the threshold, crowd in, cut in,
   drop in, edge in, elbow in, encroach, enlist, enroll, enter,
   entrench, foist in, gain admittance, get in, get into, go in,
   go into, have an entree, have an in, hop in, horn in, impinge,
   impose, impose on, impose upon, infiltrate, infringe, insert,
   insinuate, interfere, interlope, interpose, intervene, intrude,
   invade, irrupt, jam in, join, join up, jump in, league with,
   look in, obtrude, pack in, pop in, press in, push in, put in,
   put on, put upon, rush in, set foot in, sign on, sign up, slink in,
   slip in, smash in, sneak in, squeeze in, steal in, step in,
   storm in, take in, take out membership, take up membership,
   team up with, team with, throng in, thrust in, trench, trespass,
   visit, wedge in, work in, worm in