BRITNEY SPEARS made her big TV comeback last night as a lovestruck receptionist on "How I Met Your Mother" -- how did she do?

Critics are praising Britney's turn as a secretary with a crush on the show's lead, JOSH RADNOR, as his character continues his quest for his future wife, and ET got the scoop straight from the show's creators and executive producers, CRAIG THOMAS and CARTER BAYS, on working with the pop princess.

Thomas told ET that Britney helped carry the show to record ratings: "I guess the final numbers aren't in but I think it was like 10.6 million [viewers who tuned in] and we got a 4.5 in [the] 18 to 49 [demographic] which is a record -- head and shoulders a record for our series in three years -- so we're pretty excited about it."

Thomas said it was "really fun" working with Britney, saying "she did a great job." He also noted that she was very down to earth on the set: "It didn't seem like having Britney Spears on our set -- it seemed like having an actor who was doing a good job at this role -- so it all felt very normal and low-key very quickly. There was no sense of commotion and stress around it."

Bays did point out that in one respect it was different from an average week on the set: "It was an interesting week having this much paparazzi attention. We don't normally have helicopters flying over the stage."

On learning that Britney would be appearing on the show, Bays said he was surprised: "I got the call the Thursday night before we started shooting that Britney was interested and I was in my car -- I had to pull over to the side of the road [because] I couldn't believe it.

"If you had asked us to make a list of the 100 people that we saw in this role," he continued, "Britney would not have been on that list, but she called us up and I guess she heard about the part and said she wanted to do it so we were like, 'All right, sure.'"

Thomas pointed out: "It was cool having a big star call up and say, 'Well, I'm not looking to play the big role, I just want the small, funny character role,' which we admired and we thought it was great that she wanted to do something small and funny."

Will Britney return? Thomas wouldn't rule out a Britney return on the show, saying, "Anyone in the universe could come back around. We liked ending the show on Barney (NEIL PATRICK HARRIS) and Britney because it feels like maybe there's a story there. So yeah, we'd love to have her back."