Cathy Lee Crosby held Joe Theismann's hand on the ambulance ride from RFK Stadium to Arlington Hospital Monday night and stayed by his side through the long night. She was also with him through the day yesterday in his private double room as Theismann's fans inundated the hospital with flowers, balloons, get-well cards, candy and even some stuffed animals. Hospital officials don't know what they're going to do with all the gifts coming in for the Redskins quarterback as he recovers from his broken leg. One hospital spokesman said more than 50 baskets of flowers had been delivered and at least three bunches of balloons. All the gifts have been shown to Theismann, who was listed in fair condition late yesterday. Theismann has asked that in lieu of gifts and flowers, any donations should be made to the Children's Hospital Development Center. The Mouse That Moved

It's a big week in town for unusual celebrities -- Donald Duck, Mickey Mouse, Minnie Mouse, Goofy and the rest -- but what is not generally known is that the Disney characters are Teamsters. At least the people who dress up as the cartoon figures are members of the union. They're to be here for two weeks of various activities and had all been booked into the Vista International Hotel. But when Ron Richardson, secretary-treasurer of the Hotel and Restaurant Employees, Local 25, found out, he called the Disney people.

The Vista is a nonunion hotel and good card-carrying members Donald, Mickey and the gang wanted none of it. They moved up the street to the organized Madison Hotel. The Disney management, not concerned about that kind of thing, stayed at the Vista, where the Disney characters will attend a Toys for Tots Christmas party Nov. 29. Richardson was so pleased with his success in getting the characters to move into a union hotel that he said, "I'm glad to see that Mickey is a working man's mouse and not a rat." The Pizza Patrol

The House Ways and Means Committee is not a friendly place these days, especially with all the wrangling over tax reform. New York Gov. Mario Cuomo and Rep. Thomas Downey (D-N.Y.), a member of Ways and Means, have been having some differences lately over tax reform. But when you sit down over pizza, you can't have arguments. Cuomo and Downey sat down this week to Sicilian-style pizza at Prima Pizza, the restaurant Downey's wife, Chris Downey, owns on Capitol Hill.

Downey can often be found there, where his wife says he serves as "a full-time taste tester." And he often brings Ways and Means colleagues like Reps. Marty Russo and Byron Dorgan with him. End Notes

It does seem a bit early for Christmas. But the tree that will be put up on the west side of the Capitol will be cut down Friday in Ottawa National Forest at Ironwood, Mich. Sen. Donald Riegle said former Civilian Conservation Corps members who helped plant the forest will take part in felling the tree . . .

Embattled lawyer Roy Cohn is expected to be released from the National Cancer Institute this weekend after three weeks of experimental treatment. Cohn, 58, was once chief counsel to the late Sen. Joseph McCarthy. Cohn was reportedly being treated for liver cancer. Back home in New York, he is also facing disbarment proceedings . . .

Entertainer Sammy Davis Jr. was released Monday from the Cedars-Sinai Medical Center in West Hollywood, Calif., where he underwent reconstructive hip surgery. Davis expects to be recuperating for several weeks . . .