During the time when Bob was Krusty's sidekick, he'd had a tiny dressing room. Well, perhaps it was an exaggeration to call it tiny, but compared to Krusty's dressing room, Bob's room was barely bigger than a janitor's closet. Bob wouldn't have been surprised if the "Sideshow Bob" star on the door peeled off to reveal "JANITOR".
The first time Bob put on that stupid grass skirt and bone necklace, he stared at his reflection in the cracked mirror and sighed. As Bob had never been an avid viewer of Krusty's show, he didn't know whether the "Sideshows" always wore this stupid excuse for a costume, or whether Krusty was making some sort of jibe at Bob's palm tree hairstyle. At least Bob wasn't forced to wear anything in his hair, like a bone. Whether Krusty wanted to let Bob keep a fraction of his dignity, or if he thought Bob's hair was outlandish enough, Bob had no idea, and decided he would rather not know.
The skirt itched, and the necklace poked into his throat a little. Bob wouldn't complain, though. His mother would tell him it was unprofessional to complain, and that she'd worn far more uncomfortable costumes: for instance, in As You Like It, in which she'd played Rosalind, she'd worn the ridiculous sort of gown that would have been popular with Elizabethan noblewomen, complete with the huge farthingale skirt, padded sleeves, and heavy ornamentation. If his mother could cope with awful costumes, so could Bob.
Thinking of his mother made Bob eye the crack in his mirror. Judith could be superstitious at times, and could interpret such things as a cracked mirror as a sign that a performance would not go well. Bob refused to dwell on the mirror, or his discomfort. He would focus on performing. To slightly paraphrase Vesti la giubba from Pagliacci, "The people pay, and they want to laugh...laugh, clown, and the crowd will cheer!"
Bob could laugh at himself. It wouldn't kill him. He could focus on the positives of this situation: the shoes he wore fit him quite nicely, and he could make the children happy. Sure, Krusty's style of humour insulted the children's intelligence, but now that Bob was a part of this show, perhaps he could fix it up. He could talk Krusty into adding more educational content, and help him see the children as people, not just mindless meat puppets who would buy anything he endorsed.
Bob noticed that his reflection's eyes had started to sparkle with a little madness. To calm down, Bob blew into his slide whistle. He'd have to get used to that silly instrument anyway. Maybe one day, he wouldn't be forced to use the slide whistle any longer, and he could make his voice heard.
Being Krusty's sidekick wouldn't be so bad. Something good would come out of it. It might take time, but things would get better. As long as Bob could keep himself sane...