| 21 | Guess I’m Dumb- engineer:
- Chuck Britz
- producer:
- Brian Wilson
- mixer:
- Brian Wilson (in 1965)
- 12 string guitar:
- Glen Campbell (on 1964-10-14) and Carl Wilson (on 1964-10-14)
- baritone saxophone:
- Jay Migliori (on 1964-10-14)
- bell tree, drums (drum set) and timbales:
- Hal Blaine (on 1964-10-14)
- cello:
- Jesse Ehrlich (on 1964-10-14) and Anne Goodman (on 1964-10-14)
- electric bass guitar:
- Larry Knechtel (on 1964-10-14)
- electric guitar:
- Tommy Tedesco (on 1964-10-14)
- grand piano:
- Grand Piano (on 1964-10-14)
- tenor saxophone:
- Steve Douglas (on 1964-10-14)
- trombone:
- Harry Betts (on 1964-10-14) and Lou Blackburn (on 1964-10-14)
- trumpet:
- Roy Caton (on 1964-10-14) and Ollie Mitchell (on 1964-10-14)
- viola:
- Alexander Neiman (on 1964-10-14) and Darrel Terwilliger (on 1964-10-14)
- violin:
- Arnold Belnick (on 1964-10-14), James Getzoff (on 1964-10-14), Leonard Malarsky (on 1964-10-14) and Sid Sharp (on 1964-10-14)
- background vocals:
- Ginger Blake (from 1965-03-08 until 1965-04-19), Diane Rovell (from 1965-03-08 until 1965-04-19), Brian Wilson (from 1965-03-08 until 1965-04-19), Carl Wilson (from 1965-03-08 until 1965-04-19) and Marilyn Wilson (from 1965-03-08 until 1965-04-19)
- lead vocals:
- Glen Campbell (from 1965-03-08 until 1965-04-19)
- arranger:
- Brian Wilson
- recorded at:
- Western Recorders, Studio 3 in Hollywood, Los Angeles, California, United States (on 1964-10-14) and Western Recorders in Los Angeles, California, United States (from 1965-03-08 until 1965-04-19)
- mixed at:
- Western Recorders in Los Angeles, California, United States (in 1965)
- recording of:
- Guess I’m Dumb (from 1964-10-14 until 1965-04-19)
- writer:
- Russ Titelman and Brian Wilson
| Glen Campbell | | 2:44 |
