He’s just replying. “Kumbya!” was Eek’s standard cry of shock.
My submissions:
“Snap me down!” “Cut me an oversized wedge!” (same show segment)
“I am NOT overreacting! I’m a teenager!”
“Hockey-shockers!”
“Ah-HA! I love saying that. All together now: ah-HA!”
“A minor setback.” “Go forth and destroy!” (same show)
“Why’s things always falling on my head?” (a PC game)
From Schoolhouse Rock, Interjections.
From Doonesbury, Mike trying to get signatures to get John Anderson on the 1980 presidential ballot.
The Blues Brothers of course.
One I forgot- not really a catchphrase per se, but part of an online gag, sort of a web catchphrase:
“The dog ate grandma’s toes.”
And an actual Web catchphrase:
“Yeah, right…”
I don’t know if it’s what you’re going for, but “Unbelieveable!” was the catchphrase of a goofy guitar-playing guy whose name I forgot from the most recent Apprentice.
Bingo. His name is Danny Kastner.
And I’m a bit disappointed that it took so long for someone to guess that. 
Katie Kaboom, “Animaniacs”
Uncle Ted, “Bobby’s World”
Put your deeriere in your chairieaire
Put your hinny back in the reclinny
These two were lines used by the announcer when Kablam! was going to commercial.
Some other ones I thought of:
“Hooba!”
“When does the hurting stop?”
“Shaddup!” (spoken in a Jerry Lewis voice)
“Yeeeargh!” (This is an actual person, a politician. Since his utterance was spoken and not written out, I thought it was funny to see it written down. A number of sources, including the 2005 World Almanac and Book of Facts, use a spelling similar to this one.)
“When does the hurting stop?”
Bill, from Terrible Thunder Lizards, after he gets blown up or something.
“Yeeeargh!”
Howard Dean, during his Pres campaign.
How about…
“I’ve got a donk”
Marsupalami
Cal, Undergrads. Hey, Roomy Guy.
Here’s a very obscure one:
“Zip, zam, zowie and swoosh!”
Is this the infamous Orson Welles frozen peas tape? Listening to the real thing, the closest line in it is “I thought there was a slight gonk.” (“What is a gonk?” “You know, a bang from outside.”)
Since this one seems to have gotten trough – its from Sportscenter. Kenny Mayne would say it for baseball homeruns. That show has inspired more catchphrases in the last several years than any I can think of.
Yes! Man, that show was great…
That would be the late, great Wesly Willis.
Here’s one for ya (also kinda tricky):
[in a robot voice]Oh, Wesley.
Clone High, the principal’s robot butler, who inexplicably thought he was named Wesley.
I should probably add one…
From anime:
‘Nyo!’ (Appended to sentences.)