1xx informational response

• 100 Continue: Rex Spangler, the Bedazzler
• 101 Switching Protocols: Randall Mouth-Harp
• 102 Processing: Chrysler LeBaron
• 103 Early Hints: The Fishin' Physician

2xx success

• 200 OK: Gravybelly Dunstan
• 201 Created: Extra-Skin Dave
• 202 Accepted: Beanbag-Chair Bill
• 203 Non-Authoritative Information: Grant Sharpnails, the Scratcher
• 204 No Content: Tommy Lice-Comb
• 205 Reset Content: "Medicated Shampoo" Jonah Jump
• 206 Partial Content: General Woundwort, the Giant Rabbit
• 207 Multi-Status: Genius L. Cravat, the Gentleman
• 208 Already Reported: Giant Bat Wings Roland
• 226 IM Used: Texas Emil

3xx redirection

• 300 Multiple Choices: The Ornamentalist
• 301 Moved Permanently: Captain Slick-Talk
• 302 Found: Sackfist, the Tapdancing Trombo
• 303 See Other: Souvenir-Selling Mlodinow
• 304 Not Modified: Blind Buck and "Woozy," the Invisible Seeing-Eye Dog
• 305 Use Proxy: Roundhouse Farter
• 306 Switch Proxy: Red Ball Pnutz
• 307 Temporary Redirect: Fake Cockney Accent Alan Strippe
• 308 Permanent Redirect: Air and Whiskey Dale McGlue

4xx client errors

• 400 Bad Request: Ladry Jerry Lardo
• 401 Unauthorized: Low-Carb Aleks Stovepipe
• 402 Payment Required: Hugo Stares
• 403 Forbidden: Eldred Splinters
• 404 Not Found: Oliver, the Train-Oyster
• 405 Method Not Allowed: Pring, Ultralord of the Hobo Jungle
• 406 Not Acceptable: Utz, the Crab Chip
• 407 Proxy Authentication Required: Salt-and-Pepper Chest
• 408 Request Timeout: Beverly Hills Buntz
• 409 Conflict: Mississippi Barry Phlegm
• 410 Gone: Matter-Eater Brad
• 411 Length Required: 49-State Apthorp, the Alaska-Phobe
• 412 Precondition Failed: New Hampshire Todd
• 413 Payload Too Large: "Taxachusetts" Glenn
• 414 URI Too Long: Hydrocephalic Jones
• 415 Unsupported Media Type: Vermont "Greenmountain Boy" Phil Marijuana
• 416 Range Not Satisfiable: Alaska Mick the Crabber
• 417 Expectation Failed: Arizona Ludwig
• 421 Misdirected Request: Silas Swollentoe
• 422 Unprocessable Entity: Slimneck Holden Fop
• 423 Locked: Aspiring Jaster
• 424 Failed Dependency: Illinois Obama
• 425 Too Early: Sammy Austere
• 426 Upgrade Required: New Mexico Anselm Turquoise-Eater
• 428 Precondition Required: Prayerful Stan, the Bent-Knee Yahoo
• 429 Too Many Requests: Four-Fisted Jock Socko
• 431 Request Header Fields Too Large: Shadow ("Blinky") Preston
• 451 Unavailable For Legal Reasons: Somersaulting Mike Spitz

5xx server errors

• 500 Internal Server Error: The Rambling, Rambling Boris Wander
• 501 Not Implemented: Business-Class Klaus Riel
• 502 Bad Gateway: Emergency Exit Aisle Gustav Nook
• 503 Service Unavailable: Unnervingly Candid Nicky Thain
• 504 Gateway Timeout: Snoops Lightstep Trenchcoat, the Hobo PI
• 505 HTTP Version Not Supported: William Carlos Williams
• 506 Variant Also Negotiates: Beef Grease Porter Dripchin
• 507 Insufficient Storage: Exoskeleton Chester Fields
• 508 Loop Detected: Roth IRA Romeo Leeds, the Well Prepared
• 510 Not Extended: Bum-Hating Virgil Hate-Bum
• 511 Network Authentication Required: Thor the Bum-Hammer

Cross-posted from my website.